A173506 a(n) = (3^(3^n) - 1)/2.

1, 13, 9841, 3812798742493, 221713244121518884974124815309574946401

Offset: 0

Author

Roger L. Bagula, Feb 20 2010

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 0..6

Crossrefs

Cf. A051179, A173507.

Programs

Mathematica

Table[(3^(3^m) -1)/2, {m, 0, 10}]

Sage

[(3^(3^n) -1)/2 for n in (0..10)] # G. C. Greubel, Apr 25 2021

Formula

2*a(n+1) + 1 = ( 2*a(n) + 1 )^3.

Extensions

Introduced standard nomenclature in the definition, added recurrence - the Assoc. Editors of the OEIS, Feb 24 2010