A242083 a(n) = 3^p - 2^p - 1, where p is prime(n).

4, 18, 210, 2058, 175098, 1586130, 129009090, 1161737178, 94134790218, 68629840493970, 617671248800298, 450283768452043890, 36472994178147530850, 328256958598444055418, 26588814218220014932458, 19383245658672820642055730

Offset: 1

Author

Vincenzo Librandi, May 04 2014

Keywords

• nonn
• easy

Comments

For p>3, all terms are divisible by 42.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..320

Crossrefs

Cf. A000040, A083321, A204768.

Programs

Magma

[3^p-2^p-1: p in PrimesUpTo(60)];

Mathematica

Table[(3^Prime[n] - 2^Prime[n] - 1), {n, 1, 30}]
3^#-2^#-1&/@Prime[Range[20]] (* Harvey P. Dale, Aug 05 2016 *)

PARI

a(n) = my(p = prime(n)); 3^p-2^p-1; \\ Michel Marcus, May 05 2014

Sage

[3^p-2^p-1 for p in primes(60)] # Bruno Berselli, May 12 2014

Formula

a(n) = abs(A083321(A000040(n))). - Michel Marcus, May 05 2014