A165349 - OEIS

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A165349

Primes p such that (p^2-1)/4-p is also prime.

7, 11, 13, 19, 23, 29, 41, 43, 59, 73, 79, 103, 109, 113, 131, 139, 173, 181, 191, 233, 263, 271, 283, 293, 311, 313, 331, 379, 389, 401, 409, 421, 433, 439, 443, 463, 491, 499, 521, 599, 613, 631, 641, 673, 701, 719, 751, 773, 839, 859, 929, 953, 983, 991, 1033, 1039, 1063

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

FORMULA

A165557(n) = (a(n)^2-1)/4-a(n).

EXAMPLE

For p=7, (p^2-1)/4-p=5, which is prime. For p=11, (p^2-1)/4-p=19, which is prime. p=13: (p^2-1)/4-p=29.

MATHEMATICA

Select[Prime[Range[180]], PrimeQ[(#^2 - 1) / 4 - #]&] (* Vincenzo Librandi, Apr 10 2013 *)

PROG