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A364926

Prime powers (A000961) q such that 2*q+1 is a prime.

1, 2, 3, 5, 8, 9, 11, 23, 29, 41, 53, 81, 83, 89, 113, 125, 128, 131, 173, 179, 191, 233, 239, 243, 251, 281, 293, 359, 419, 431, 443, 491, 509, 593, 641, 653, 659, 683, 719, 729, 743, 761, 809, 911, 953, 1013, 1019, 1031, 1049, 1103, 1223, 1229, 1289, 1331, 1409, 1439, 1451, 1481, 1499

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OFFSET

1,2

LINKS

Jianing Song, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = (A048184(n)-1)/2.

EXAMPLE

9 is a term since 9 = 3^2 and that 2*9+1 = 19 is prime.

MATHEMATICA

q[k_] := (k == 1 || PrimePowerQ[k]) && PrimeQ[2*k+1]; Select[Range[1500], q] (* Amiram Eldar, Mar 18 2026 *)

PROG