A051899 - OEIS

A051899

Smallest prime p such that (p-1)/(2*n) is also a prime.

5, 13, 13, 17, 31, 37, 29, 113, 37, 41, 67, 73, 53, 197, 61, 97, 103, 73, 191, 281, 127, 89, 139, 97, 101, 157, 109, 113, 1103, 181, 311, 193, 199, 137, 211, 937, 149, 229, 157, 241, 1559, 421, 173, 617, 181, 277, 283, 193, 197, 701, 307, 313, 743, 541, 331

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OFFSET

1,1

LINKS

David A. Corneth, Table of n, a(n) for n = 1..10000

FORMULA

(a(n)-1)/2n = A051686(n), the smallest 2k-Germain primes.

EXAMPLE

a(2) = 13 because (13 - 1)/4 = 3 = A051686(2);

a(3) = 13 as well, because (13 - 1)/6 = 2 = A051686(3);

a(8) = 113 because (113 - 1)/16 = 7 is a prime.

PROG