A171574 Primes of the form p=floor(T/4), T are Triangular numbers.

2, 3, 5, 7, 11, 13, 19, 47, 101, 157, 331, 457, 569, 1069, 1237, 1471, 1667, 2161, 2467, 2719, 3061, 3719, 4027, 4441, 5227, 5591, 6469, 6991, 7411, 9011, 11287, 14407, 15797, 16607, 18097, 21269, 21997, 24697, 29221, 30319, 32321, 35311, 38711

Offset

1,1

Links

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

Example

floor(10/4)=2, floor(15/4)=3, floor(21/4)=5,..

Mathematica

f[n_]:=n*(n+1)/2; lst={}; Do[If[PrimeQ[p=Floor[f[n]/4]], AppendTo[lst, p]], {n, 7!}]; lst
Select[Floor[Accumulate[Range[600]]/4], PrimeQ] (* Harvey P. Dale, Nov 09 2022 *)

Crossrefs

Cf. A000217

Sequence in context: A362850 A338396 A067910 * A354800 A280937 A296236

Adjacent sequences: A171571 A171572 A171573 * A171575 A171576 A171577

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Dec 12 2009

Status

approved