A171739 a(n) = 2^(n*(n-1)/2)*3^(n*(n+1)/2).

1, 3, 54, 5832, 3779136, 14693280768, 342764853755904, 47976111050506371072, 40290721869103654477234176, 203018823308689211155302473269248, 6137885950748052085508841340966822477824, 1113403476497577147178633950236927694314586243072

Offset: 0

Author

Michael Somos, Dec 17 2009

Keywords

• nonn
• easy

Examples

			1 + 3*x + 54*x^2 + 5832*x^3 + 3779136*x^4 + 14693280768*x^5 + 342764853755904*x^6 + ...
		

Links

• Vincenzo Librandi, Table of n, a(n) for n = 0..50

Crossrefs

Cf. A081955.

Programs

Maple

A171739:=n->2^(n*(n-1)/2)*3^(n*(n+1)/2): seq(A171739(n), n=0..15); # Wesley Ivan Hurt, Feb 12 2017

Mathematica

Table[2^(n*(n-1)/2) * 3^(n*(n+1)/2), {n, 0, 20}] (* Vincenzo Librandi, Jan 03 2013 *)

PARI

{a(n) = 2^(n*(n-1)/2) * 3^(n*(n+1)/2)}

Formula

a(-n) = A081955(n).

a(n+1)*a(n-1) = 6*a(n)^2.

G.f.: 1 / (1 - 6^1 / 2 * x / (1 - (6^1 - 1) * 6^1 / 2 * x / (1 - 6^2 / 2 * x / (1 - (6^2 - 1) * 6^2 / 2 * x / ... )))). - Michael Somos, Jan 03 2013