A068219 Denominators of coefficients in log(1+x)*(1+x)^(1/3) power series.

3, 3, 9, 3, 15, 9, 21, 6, 27, 15, 33, 9, 39, 21, 45, 12, 51, 27, 57, 15, 63, 33, 69, 18, 75, 39, 81, 21, 87, 45, 93, 24, 99, 51, 105, 27, 111, 57, 117, 30, 123, 63, 129, 33, 135, 69, 141, 36, 147, 75, 153, 39, 159, 81, 165, 42, 171, 87, 177, 45, 183, 93, 189, 48, 195, 99

Offset

1,1

Comments

log(1+x)*(1+x)^(1/3) = (-4)*sum(k=>1,(-x)^k/(3k))

Links

G. C. Greubel, Table of n, a(n) for n = 1..10000

Formula

a(n) = 3*n if n==1 or 3 (mod 4), a(n) = 3*n/2 if n==2 (mod 4), a(n) = 3*n/4 if n==0 (mod 4).

a(n) = 3*A060819(n). - Mitch Harris, Jun 29 2005

Mathematica

fn[n_]:=Module[{m=Mod[n, 4]}, Which[OddQ[m], 3n, m==2, 3 n/2, True, 3 n/4]]; Array[fn, 70] (* Harvey P. Dale, Sep 18 2012 *)

Crossrefs

Sequence in context: A339318 A359600 A166466 * A337461 A157031 A113213

Adjacent sequences: A068216 A068217 A068218 * A068220 A068221 A068222

Keyword

easy,frac,nonn

Author

Benoit Cloitre, Mar 30 2002

Status

approved