A178424 17 followed by the base-18 Fermat numbers.

17, 19, 325, 104977, 11019960577, 121439531096594251777, 14747559712960682275277163588165279154177, 217490517487340961382742893166950969620647214876916403331613367885781133978238

Offset

0,1

Links

Table of n, a(n) for n=0..7.

Formula

a(n) = 18^(2^(n-1))+1, n > 0.

a(n) = 2 + Product_{i=0..n-1} a(i).

a(n) = 1 + (a(n-1)-1)^2, n > 1.

Product_{n>=0} (1 - 1/a(n)) = 8/9. - Amiram Eldar, Dec 01 2025

Mathematica

a[0] := 17;
a[n_] := a[n] = Product[a[i], {i, 0, n - 1}] + 2;
Table[a[n], {n, 0, 10}]

Crossrefs

Cf. A000215.

Sequence in context: A132242 A162873 A174379 * A068387 A372220 A134539

Adjacent sequences: A178421 A178422 A178423 * A178425 A178426 A178427

Keyword

nonn,easy

Author

Roger L. Bagula, May 27 2010

Extensions

Edited by the Assoc. Eds. of the OEIS, Jul 20 2010

Status

approved