A140853 a(n) = prime(prime(n) - 1) - 1, where prime(n) is the n-th prime.

1, 2, 6, 12, 28, 36, 52, 60, 78, 106, 112, 150, 172, 180, 198, 238, 270, 280, 316, 348, 358, 396, 420, 456, 502, 540, 556, 576, 592, 612, 700, 732, 768, 786, 856, 862, 910, 952, 982, 1020, 1060, 1068, 1150, 1162, 1192, 1212, 1290, 1398, 1428, 1438, 1458

Offset: 1

Author

Juri-Stepan Gerasimov, Jul 30 2008

Keywords

• nonn
• easy

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A006093, A055003.

Programs

Mathematica

Table[Prime[Prime[n - 1] - 1] - 1, {n, 2, 60}] (* Vincenzo Librandi, Apr 05 2015 *)

PARI

apply(p->prime(p-1)-1, primes(100))

Formula

a(n) = A055003(n) - 1. - N. J. A. Sloane, Jul 31 2008

a(n) ~ n (log n)^2. - Charles R Greathouse IV, Apr 07 2015

Extensions

Corrected (382 replaced by 396) and extended by R. J. Mathar, Apr 27 2010