0,3

Table of n, a(n) for n=0..79.

a(n)= binomial ((A000120(n-1)+A023416(n-1)), A000120(n-1)).

a(0)=1 because 0 (or 0 written in base 2), a(1)=1 because 1 (or 1 written in base 2), a(3)= 2 (or 10 written in base 2) and (01,10)=distinct transpositions.

Cf. A001477.

Sequence in context: A124770 A099246 A039775 * A227532 A152534 A136018

Adjacent sequences: A178241 A178242 A178243 * A178245 A178246 A178247

nonn,base

Juri-Stepan Gerasimov, May 23 2010

Corrected (a 3 in the first group removed) by R. J. Mathar, May 28 2010

approved