A174230 a(n) = product_{i=1..n-1} a(i), with a(1) = 3 and a(2) = 7.

3, 7, 21, 441, 194481, 37822859361, 1430568690241985328321, 2046526777500669368329342638102622164679041, 4188271851027274266670020743752976432915773724299403513508038881183728210190544679681

Offset

1,1

Comments

Except for first two terms a(n) = 21^2^n

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

Links

Table of n, a(n) for n=1..9.

Mathematica

Join[{3, 7}, NestList[#^2&, 21, 7]] (* Harvey P. Dale, Jan 18 2012 *)

Crossrefs

Cf. A175138.

Sequence in context: A169981 A191294 A177820 * A158236 A174942 A128599

Adjacent sequences: A174227 A174228 A174229 * A174231 A174232 A174233

Keyword

nonn

Author

Giovanni Teofilatto, Mar 15 2010

Status

approved