Special neighbor primes: Difference between revisions
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73 + 79 - 1 = 151
</pre>
=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
Uses the [[Extensible_prime_generator#Delphi|Delphi Prime-Generator Object]]
<syntaxhighlight lang="Delphi">
procedure SpecialNeighborPrimes(Memo: TMemo);
var I: integer;
var P1,P2: integer;
var Sieve: TPrimeSieve;
begin
Sieve:=TPrimeSieve.Create;
try
{Build more primes than we need}
Sieve.Intialize(200);
{Go through all primes}
for I:=1 to High(Sieve.Primes) do
begin
{Get neighbor primes}
P1:=Sieve.Primes[I-1];
P2:=Sieve.Primes[I];
{only test up to 100}
if P2>=100 then break;
{if P1+P2-1 is prime then display}
if Sieve.Flags[P1 + P2 - 1] then Memo.Lines.Add(Format('(%d, %d)',[P1,P2]));
end;
finally Sieve.Free; end;
end;
</syntaxhighlight>
{{out}}
<pre>
(3, 5)
(5, 7)
(7, 11)
(11, 13)
(13, 17)
(19, 23)
(29, 31)
(31, 37)
(41, 43)
(43, 47)
(61, 67)
(67, 71)
(73, 79)
Elapsed Time: 9.926 ms.
</pre>
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