A232460 a(n) = 2^(2^n) - 5.

-3, -1, 11, 251, 65531, 4294967291, 18446744073709551611, 340282366920938463463374607431768211451, 115792089237316195423570985008687907853269984665640564039457584007913129639931

Offset: 0

Author

Arkadiusz Wesolowski, Nov 24 2013

Keywords

• sign
• easy

Comments

For n >= 3, a(n) is not of the form 2^k + p, where p is a prime. Therefore every term greater than 11 is in A006285 (de Polignac numbers).

Links

• Wacław Sierpiński, Elementary Theory of Numbers, Monografie Matematyczne 42 (1964), p. 415.

Crossrefs

Cf. A006285.

Programs

Magma

[2^(2^n)-5 : n in [0..8]]

Mathematica

Table[2^(2^n) - 5, {n, 0, 8}]

PARI

for(n=0, 8, print1(2^(2^n)-5, ", "));

Python

def A232460(n): return (1<<(1<Chai Wah Wu, Jul 19 2022

Formula

a(n) = A000215(n) - 6.

a(0) = - 3; a(n) = (a(n-1) + 5)^2 - 5, n >= 1.