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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.
Sequence in context: A264154 A099246 A039775 * A227532 A152534 A136018
Adjacent sequences: A178241 A178242 A178243 * A178245 A178246 A178247
Juri-Stepan Gerasimov, May 23 2010
Corrected (a 3 in the first group removed) by R. J. Mathar, May 28 2010