A163579 Primes of the form floor(k*(k+1)*Pi/2), k>=0, where Pi = 3.1415.. = A000796.

3, 31, 47, 113, 659, 1021, 1187, 1979, 2971, 3251, 5749, 9679, 10433, 14627, 20593, 22807, 23957, 35107, 39461, 55813, 58207, 109063, 152417, 157349, 201881, 227419, 244463, 262121, 292469, 295187, 310357, 318793, 320209, 323053, 328777, 333103

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Jul 31 2009

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Programs

Mathematica

s=0;lst={};Do[s+=n;p=IntegerPart[s];If[PrimeQ[p],AppendTo[lst,p]],{n,0,7!,Pi}];lst
Select[Floor[Accumulate[Range[800]]*Pi],PrimeQ] (* Harvey P. Dale, Nov 20 2018 *)

PARI

for(n=1,500, m=floor(n*(n+1)*Pi/2); if(isprime(m), print1(m, ", "))) \\ G. C. Greubel, Jul 28 2017

Extensions

Definition clarified by R. J. Mathar, Sep 24 2011