Successive prime differences: Difference between revisions
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Last group: { 997141 997147 997151 997153 } |
Last group: { 997141 997147 997151 997153 } |
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Count: 306 |
Count: 306 |
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</pre> |
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=={{header|FreeBASIC}}== |
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<lang freebasic>#include "isprime.bas" |
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function nextprime( n as uinteger ) as uinteger |
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'finds the next prime after n |
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if n = 0 then return 2 |
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if n < 3 then return n + 1 |
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dim as integer q = n + 2 |
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while not isprime(q) |
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q+=2 |
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wend |
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return q |
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end function |
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function spd( byval n as integer, d() as integer ) as boolean |
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if not isprime(n) then return false |
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for i as integer = lbound(d) to ubound(d) |
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if not nextprime(n) = n + d(i) then return false |
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n+=d(i) |
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next i |
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return true |
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end function |
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sub print_set( byval n as uinteger, d() as uinteger ) |
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print "( ";n;" "; |
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for i as integer = lbound(d) to ubound(d) |
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print n+d(i);" "; |
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n+=d(i) |
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next i |
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print ")" |
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end sub |
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function count_below( max as uinteger, d() as uinteger ) as uinteger |
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dim as uinteger c = 0, last = 0 |
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for n as uinteger = 2 to max-d(ubound(d)) |
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if spd(n, d()) then |
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c+=1 |
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if c=1 then print_set( n, d() ) |
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last = n |
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end if |
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next n |
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print_set(last, d()) |
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return c |
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end function |
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dim as integer n, c |
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'example 1, differences of 2 |
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redim as uinteger d(0) |
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d(0) = 2 |
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print "Differences of 2 (the twin primes)" |
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c = count_below(1000000, d()) |
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print "Number of occurrences: ", c |
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'example 2, difference of 1 |
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d(0) = 1 |
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print |
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print "Differences of 1" |
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c = count_below(1000000, d()) |
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print "Number of occurrences: ", c |
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'example 3, differences of 2,2 |
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redim as uinteger d(1) |
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d(0) = 2 : d(1) = 2 |
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print |
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print "Differences of 2, 2" |
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c = count_below(1000000, d()) |
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print "Number of occurrences: ", c |
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'example 4, differences of 2,4 |
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d(1) = 4 |
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print |
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print "Differences of 2, 4" |
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c = count_below(1000000, d()) |
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print "Number of occurrences: ", c |
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'example 5, differences of 2,2 |
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d(0) = 4 : d(1) = 2 |
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print |
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print "Differences of 4, 2" |
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c = count_below(1000000, d()) |
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print "Number of occurrences: ", c |
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'example 6, differences of 6,4,2 |
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redim as uinteger d(2) |
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d(0) = 6 : d(1) = 4 : d(2) = 2 |
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print |
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print "Differences of 6, 4, 2" |
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c = count_below(1000000, d()) |
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print "Number of occurrences: ", c</lang> |
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{{out}}<pre> |
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Differences of 2 (the twin primes) |
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( 3 5 ) |
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( 999959 999961 ) |
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Number of occurrences: 8169 |
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Differences of 1 |
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( 2 3 ) |
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( 2 3 ) |
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Number of occurrences: 1 |
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Differences of 2, 2 |
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( 3 5 7 ) |
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( 3 5 7 ) |
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Number of occurrences: 1 |
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Differences of 2, 4 |
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( 5 7 11 ) |
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( 999431 999433 999437 ) |
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Number of occurrences: 1393 |
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Differences of 4, 2 |
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( 7 11 13 ) |
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( 997807 997811 997813 ) |
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Number of occurrences: 1444 |
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Differences of 6, 4, 2 |
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( 31 37 41 43 ) |
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( 997141 997147 997151 997153 ) |
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Number of occurrences: 306 |
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</pre> |
</pre> |
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Number found = 306 |
Number found = 306 |
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</pre> |
</pre> |
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=={{header|Haskell}}== |
=={{header|Haskell}}== |
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Uses primes library: http://hackage.haskell.org/package/primes-0.2.1.0/docs/Data-Numbers-Primes.html |
Uses primes library: http://hackage.haskell.org/package/primes-0.2.1.0/docs/Data-Numbers-Primes.html |
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