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

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

Offset

0,1

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

Table of n, a(n) for n=0..8.

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

Formula

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

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

Mathematica

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

Prog

(Magma) [2^(2^n)-5 : n in [0..8]]
(PARI) for(n=0, 8, print1(2^(2^n)-5, ", "));
(Python)
def A232460(n): return (1<<(1<<n))-5 # Chai Wah Wu, Jul 19 2022

Crossrefs

Cf. A006285.

Sequence in context: A002589 A048522 A365035 * A337205 A287197 A118020

Adjacent sequences: A232457 A232458 A232459 * A232461 A232462 A232463

Keyword

sign,easy

Author

Arkadiusz Wesolowski, Nov 24 2013

Status

approved