Frobenius numbers: Difference between revisions

=={{header|Delphi}}==

{{works with|Delphi|6.0}}

{{libheader|SysUtils,StdCtrls}}

<syntaxhighlight lang="Delphi">

function IsPrime(N: integer): boolean;

{Optimised prime test - about 40% faster than the naive approach}

var I,Stop: integer;

begin

if (N = 2) or (N=3) then Result:=true

else if (n <= 1) or ((n mod 2) = 0) or ((n mod 3) = 0) then Result:= false

else

begin

I:=5;

Stop:=Trunc(sqrt(N));

Result:=False;

while I<=Stop do

begin

if ((N mod I) = 0) or ((N mod (i + 2)) = 0) then exit;

Inc(I,6);

end;

Result:=True;

end;

end;

function GetNextPrime(Start: integer): integer;

{Get the next prime number after Start}

begin

repeat Inc(Start)

until IsPrime(Start);

Result:=Start;

end;

procedure ShowFrobeniusNumbers(Memo: TMemo);

var N,N1,FN,Cnt: integer;

begin

N:=2;

Cnt:=0;

while true do

begin

Inc(Cnt);

N1:=GetNextPrime(N);

FN:=N * N1 - N - N1;

N:=N1;

if FN>10000 then break;

Memo.Lines.Add(Format('%2d = %5d',[Cnt,FN]));

end;

end;

</syntaxhighlight>

{{out}}

<pre>

1 = 1

2 = 7

3 = 23

4 = 59

5 = 119

6 = 191

7 = 287

8 = 395

9 = 615

10 = 839

11 = 1079

12 = 1439

13 = 1679

14 = 1931

15 = 2391

16 = 3015

17 = 3479

18 = 3959

19 = 4619

20 = 5039

21 = 5615

22 = 6395

23 = 7215

24 = 8447

25 = 9599

</pre>