A173501 a(1) = 2, a(2) = 3, a(n) = 6^(2^(n-3)) for n >= 3.

2, 3, 6, 36, 1296, 1679616, 2821109907456, 7958661109946400884391936, 63340286662973277706162286946811886609896461828096

Offset: 1

Author

Giovanni Teofilatto, Feb 20 2010

Keywords

• nonn

Comments

Except for first three terms, a(n) = (a(n-1))^2.

Essentially the same as A165424. - R. J. Mathar, Feb 21 2010

Links

• G. C. Greubel, Table of n, a(n) for n = 1..13

Crossrefs

Cf. A000079, A000400, A165424.

Programs

Mathematica

Table[If[n<3, n+1, 6^(2^(n-3))], {n,10}] (* G. C. Greubel, Apr 25 2021 *)

PARI

a(n) = if(n<=2, n+1, 6^(2^(n-3))) \\ Felix Fröhlich, Apr 25 2021

SageMath

[2,3]+[6^(2^(n-3)) for n in (3..10)] # G. C. Greubel, Apr 25 2021

Formula

a(n) = Product_{i=1..n-1} a(i) with a(1) = 2 and a(2) = 3.

a(n) = 6^(2^(n-3)) = A000400(A000079(n-3)) for n>2.

Extensions

Definition corrected by Glenn Tesler, Aug 19 2017