Primes which contain only one odd digit: Difference between revisions
Primes which contain only one odd digit (view source)
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Found 46,708 one-odd-digit primes < 10^8 (100,000,000)
Found 202,635 one-odd-digit primes < 10^9 (1,000,000,000)</pre>
=={{header|Delphi}}==
{{works with|Delphi|6.0}}
{{libheader|SysUtils,StdCtrls}}
<syntaxhighlight lang="Delphi">
function IsPrime(N: int64): boolean;
{Fast, optimised prime test}
var I,Stop: int64;
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+0.0));
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;
procedure GetDigits(N: integer; var IA: TIntegerDynArray);
{Get an array of the integers in a number}
var T: integer;
begin
SetLength(IA,0);
repeat
begin
T:=N mod 10;
N:=N div 10;
SetLength(IA,Length(IA)+1);
IA[High(IA)]:=T;
end
until N<1;
end;
procedure ShowOneOddDigitPrime(Memo: TMemo);
var I,Cnt1,Cnt2: integer;
var IA: TIntegerDynArray;
var S: string;
function HasOneOddDigit(N: integer): boolean;
var I,Odd: integer;
begin
Odd:=0;
GetDigits(N,IA);
for I:=0 to High(IA) do
if (IA[I] and 1)=1 then Inc(Odd);
Result:=Odd=1;
end;
begin
Cnt1:=0; Cnt2:=0;
S:='';
for I:=0 to 1000000-1 do
if IsPrime(I) then
if HasOneOddDigit(I) then
begin
Inc(Cnt1);
if I<1000 then
begin
Inc(Cnt2);
S:=S+Format('%4D',[I]);
If (Cnt2 mod 5)=0 then S:=S+CRLF;
end;
end;
Memo.Lines.Add(S);
Memo.Lines.Add('Count < 1,000 = '+IntToStr(Cnt2));
Memo.Lines.Add('Count < 1,000,000 = '+IntToStr(Cnt1));
end;
</syntaxhighlight>
{{out}}
<pre>
3 5 7 23 29
41 43 47 61 67
83 89 223 227 229
241 263 269 281 283
401 409 421 443 449
461 463 467 487 601
607 641 643 647 661
683 809 821 823 827
829 863 881 883 887
Count < 1,000 = 45
Count < 1,000,000 = 2560
Elapsed Time: 171.630 ms.
</pre>
=={{header|F_Sharp|F#}}==
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