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A171600 Primes of the form floor(T/8) where T is a triangular number. 1
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 20 18:52 EDT 2019. Contains 327245 sequences. (Running on oeis4.)