A242084 5^p - 4^p - 1, where p is prime.

8, 60, 2100, 61740, 44633820, 1153594260, 745759583940, 18798608421180, 11850560210900460, 185976284546943991380, 4652001187058965190220, 72740686675902780452348340, 45469899385367953379053128420

Offset: 1

Author

Vincenzo Librandi, May 04 2014

Keywords

• nonn
• less

Comments

For p>3 all terms are divisible by 21.

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..100

Crossrefs

Cf. A204768.

Programs

Magma

[5^p-4^p-1: p in PrimesUpTo(60)];

Mathematica

Table[5^Prime[n] - 4^Prime[n] - 1, {n, 1, 60}]

PARI

a(n) = my(p = prime(n)); 5^p - 4^p - 1; \\ Michel Marcus, May 05 2014

Formula

a(n) = A054401(A000040(n)). - Michel Marcus, May 05 2014