A171595 Primes of the form p=floor(T/6), T are triangular numbers.

2, 3, 7, 11, 13, 17, 31, 67, 157, 229, 379, 487, 1291, 1621, 3217, 3727, 4051, 4621, 6007, 7129, 7879, 9157, 9661, 10531, 11071, 12577, 13567, 15877, 16987, 23629, 24979, 28081, 31981, 32917, 39847, 46687, 51679, 54877, 56101, 58171, 61561

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

Floor(15/6)=2, floor(21/6)=3, floor(45/6)=7,..

Mathematica

f[n_]:=n*(n+1)/2; lst={}; Do[If[PrimeQ[p=Floor[f[n]/6]], AppendTo[lst, p]], {n, 7!}]; lst
Select[Floor[#/6]&/@Accumulate[Range[1000]], PrimeQ] (* Harvey P. Dale, Jul 23 2012 *)

Crossrefs

Cf. A000217, A171574

Sequence in context: A278698 A023221 A127430 * A106483 A145673 A321657

Adjacent sequences: A171592 A171593 A171594 * A171596 A171597 A171598

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Dec 12 2009

Status

approved