A186294 (A007519(n)+1)/2.

9, 21, 37, 45, 49, 57, 69, 97, 117, 121, 129, 141, 157, 169, 177, 201, 205, 217, 225, 229, 261, 285, 289, 297, 301, 309, 321, 337, 381, 385, 405, 429, 441, 465, 469, 477, 489, 505, 517, 525, 549, 565, 577, 597, 601, 609, 625, 645, 649, 661, 681

Offset: 1

Author

Marco Matosic, Feb 17 2011

Keywords

• nonn

Programs

PARI

isok(n) = (n % 4 == 1) && isprime(2*n-1) \\ Michel Marcus, Jul 16 2013

Extensions

More terms from Michel Marcus, Jul 16 2013