A067623 Consider the power series (x+1)^(1/3)=1+x/3-x^2/9+5x^3/81+...; sequence gives denominators of coefficients.

1, 3, 9, 81, 243, 729, 6561, 19683, 59049, 1594323, 4782969, 14348907, 129140163, 387420489, 1162261467, 10460353203, 31381059609, 94143178827, 2541865828329, 7625597484987, 22876792454961, 205891132094649, 617673396283947

Offset

0,2

Comments

All terms are powers of 3.

Links

Table of n, a(n) for n=0..22.

Formula

a(n) = 3^A004128(n).

a(n) = 3^n*a(floor(n/3)). - Vladeta Jovovic, Mar 01 2004

a(n) = denominator(binomial(1/3, n)). - Peter Luschny, Apr 07 2016

Maple

A067623 := n -> denom(binomial(1/3, n)):
seq(A067623(n), n=0..21); # Peter Luschny, Apr 07 2016

Mathematica

Table[Denominator@ Binomial[1/3, n], {n, 0, 22}] (* Michael De Vlieger, Apr 07 2016 *)

Crossrefs

Cf. A004128, A046161, A067622 (numerators), A123854.

Sequence in context: A139731 A259986 A124049 * A171557 A055156 A047912

Adjacent sequences: A067620 A067621 A067622 * A067624 A067625 A067626

Keyword

nonn,frac

Author

Benoit Cloitre, Feb 02 2002

Status

approved