A115249 -id:A115249 - cp's OEIS frontend

A005123 Numbers k such that 8k + 1 is prime.

2, 5, 9, 11, 12, 14, 17, 24, 29, 30, 32, 35, 39, 42, 44, 50, 51, 54, 56, 57, 65, 71, 72, 74, 75, 77, 80, 84, 95, 96, 101, 107, 110, 116, 117, 119, 122, 126, 129, 131, 137, 141, 144, 149, 150, 152, 156, 161, 162, 165, 170, 176, 179, 185, 186, 194, 200, 201

Offset: 1

N. J. A. Sloane

nonn

4*a(n) is the degree of the minimal polynomial of 2*cos(Pi/A007519(n)), called C(A007519(n), x) in A187360. - Wolfdieter Lang, Oct 24 2013

T. D. Noe, Table of n, a(n) for n = 1..1000

Cf. A007519, A111174, A115249.

[n: n in [0..200] | IsPrime(8*n+1)]; // Vincenzo Librandi, Jun 25 2014

Select[Range[0, 300], PrimeQ[8 # + 1] &] (* Vincenzo Librandi, Jun 25 2014 *)

is(n)=isprime(8*n+1) \\ Charles R Greathouse IV, Apr 29 2015

a(n) = (A007519(n)-1)/8. - Zak Seidov, Sep 26 2007

More terms from Wesley Ivan Hurt, Jun 25 2014

A115248 Values such that A115247(a(n))=1. Values such that A001935(a(n))==2 (mod 4).

Original entry on oeis.org

2, 5, 9, 11, 12, 14, 17, 19, 24, 29, 30, 32, 35, 39, 42, 44, 46, 50, 51, 53, 54, 56, 57, 65, 71, 72, 74, 75, 77, 80, 82, 84, 95, 96, 100, 101, 104, 107, 109, 110, 116, 117, 119, 122, 126, 127, 128, 129, 131, 137, 141, 144, 149, 150, 152, 154, 156, 161, 162, 165, 170

Offset: 0

Christian G. Bower, Jan 17 2006

nonn

All values are the sum of a triangular number A000217 and a square A000290.

K. Alladi, Partition Identities Involving Gaps and Weights, Transactions of the American Mathematical Society, Vol. 349, No. 12, Dec 1997, pp. 5001-5019.

Cf. A005123, A115249.

cp's OEIS Frontend

A005123 Numbers k such that 8k + 1 is prime.

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