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Carmichael 3 strong pseudoprimes: Difference between revisions
Carmichael 3 strong pseudoprimes (view source)
Revision as of 08:00, 11 December 2012
, 11 years ago→numbers in order of calculation: optimized code. -- ~~~~
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<br>the '''modulus''' function was hard-coded below (when using a negative value).
===numbers in order of calculation===
<lang rexx>/*REXX program
numeric digits 30 /*in case user wants bigger nums.*/
parse arg N .; if N=='' then N=61 /*allow user to specify the limit*/
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!.=0 /*a method of prime memoization. */
do p=3 to N by 2; if \isPrime(p) then iterate /*Not prime? Skip.*/
pm=p-1;
do h3=2 to pm; g=h3+p /*find Carmichael #s for this P. */
do d=1 to g-1
if g*pm//d\==0
if \isPrime(r) then iterate
carms=carms+1 /*bump the Carmichael # counter. */
min=min(min,q); max=max(max,q); @.q=r /*build a list.*/
end /*d*/
end /*h3*/
/*display a list of some Carm #s.*/
do j=min to max by 2; if @.j==0 then iterate /*one of the #s?*/
say '──────── a Carmichael number: ' p times j times @.j
end /*j*/
say /*show bueatification blank line.*/
end
say; say carms ' Carmichael numbers found.'
exit /*stick a fork in it, we're done.*/
/*──────────────────────────────────ISPRIME subroutine──────────────────*/
isPrime: procedure expose !.; parse arg x; if !.x then return 1
if wordpos(x,'2 3 5 7 11 13')\==0 then do; !.x=1; return 1; end
if x<
if right(x,1)==5 then return 0;
do i=11 by 6 until i*i>x; if x// i ==0 then return 0
if x//(i+2) ==0 then return 0
end /*i*/
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