A171600 Primes of the form floor(T/8) where T is a triangular number.

2, 3, 5, 11, 13, 17, 19, 23, 31, 37, 43, 47, 83, 97, 107, 199, 293, 337, 467, 523, 631, 643, 877, 907, 937, 953, 1097, 1181, 1453, 1511, 1753, 2081, 2437, 3011, 3407, 3797, 4241, 4273, 4339, 4987, 5023, 5347, 5531, 6221, 6581, 6703, 7331, 7417, 7547, 8167, 9001

Offset

1,1

Comments

11, 13, 17, 19, 23 together with primes of the form 16n^2 + 9n + 1, 16n^2 + 11n + 1, 16n^2 + 13n + 2, 16n^2 + 15n + 3, 16n^2 + 17n + 4, 16n^2 + 19n + 5, 16n^2 + 21n + 6, or 16n^2 + 23n + 8. - Charles R Greathouse IV, Apr 13 2012

Links

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

Example

Floor(21/8)=2, floor(28/8)=3, floor(45/8)=5,..

Mathematica

f[n_]:=n*(n+1)/2; lst={}; Do[If[PrimeQ[p=Floor[f[n]/8]], AppendTo[lst, p]], {n, 7!}]; lst
Select[Floor[#/8]&/@Accumulate[Range[500]], PrimeQ] (* Harvey P. Dale, Jul 13 2016 *)

Crossrefs

Cf. A000217, A171574, A171595

Sequence in context: A115653 A042997 A220815 * A126148 A264866 A038933

Adjacent sequences: A171597 A171598 A171599 * A171601 A171602 A171603

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Dec 12 2009

Status

approved