0,2

Only numbers in A001764 not divisible by 3 are: A001764((3^n-1)/2) for n>=0.

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

(PARI) a(n)=binomial(3^(n+1)-3, 3^n-1)/(2*3^n-1)

Cf. A001764; A135759.

Adjacent sequences: A135757 A135758 A135759 this_sequence A135761 A135762 A135763

Sequence in context: A086509 A068161 A116313 this_sequence A003541 A086829 A115976

nonn

Paul D. Hanna (pauldhanna(AT)juno.com), Dec 02 2007