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A171574 Primes of the form p=floor(T/4), T are Triangular numbers. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..43.

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

CROSSREFS

Cf. A000217

Sequence in context: A275272 A329954 A067910 * A280937 A296236 A334041

Adjacent sequences:  A171571 A171572 A171573 * A171575 A171576 A171577

KEYWORD

nonn

AUTHOR

Vladimir Joseph Stephan Orlovsky, Dec 12 2009

STATUS

approved

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Last modified July 12 08:23 EDT 2020. Contains 335657 sequences. (Running on oeis4.)