A109273 Numbers k such that k+1 is the smallest prime factor of k^3 + 3^k.

1, 4, 10, 16, 22, 28, 40, 52, 58, 70, 88, 100, 112, 130, 136, 148, 196, 232, 238, 250, 256, 280, 310, 316, 352, 382, 400, 418, 430, 442, 478, 490, 556, 562, 592, 598, 616, 640, 682, 742, 772, 796, 808, 820, 862, 880, 928, 970, 976, 1030, 1048, 1060, 1096, 1102

Offset: 1

Author

Zak Seidov and Max Alekseyev, Jun 25 2005

Keywords

• nonn

Comments

Except for the first term, 2k+1 is composite.

Crossrefs

Cf. A001585.

Programs

PARI

isok(n) = factor(n^3+3^n)[1, 1] == (n+1); \\ Michel Marcus, Oct 06 2013