Initial data commit

Task/Factorial-primes/Delphi/factorial-primes.delphi

@@ -0,0 +1,56 @@
+function IsPrime(N: int64): 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*1.0));
+	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;
+
+
+function Factorial(N: Word): int64;
+var  I: integer;
+begin
+Result:= 1;
+for I := 2 to N do Result:=Result * I;
+end;
+
+
+procedure ShowFactorialPrimes(Memo: TMemo);
+{Show factorials where F+1 or F-1 are prime}
+var I,Cnt: integer;
+var F: int64;
+
+	procedure DisplayItem(Minus: boolean);
+	var S: string;
+	var Sign: char;
+	var F1: int64;
+	begin
+	Inc(Cnt);
+	if Minus then F1:=F-1 else F1:=F+1;
+	if Minus then Sign:='-' else Sign:='+';
+	S:=Format('%2d:   %3d! %s 1 = %d',[Cnt,I,Sign,F1]);
+	Memo.Lines.Add(S);
+	end;
+
+begin
+Cnt:=0;
+for I:=1 to High(Integer) do
+	begin
+	F:=Factorial(I);
+	if IsPrime(F+1) then DisplayItem(False);
+	if IsPrime(F-1) then DisplayItem(True);
+	if Cnt>=10 then break;
+	end;
+end;