G.f.: A(x) = exp( Sum_{n>=1} A000172(n)*x^n/(2*n) ) where Franel number A000172(n) = Sum_{k=0..n} C(n,k)^3.

A166991

G.f.: A(x) = exp( Sum_{n>=1} A000172(n)*x^n/(2*n) ) where Franel number A000172(n) = Sum_{k=0..n} C(n,k)^3.

Terms

    a(0) =1a(1) =1a(2) =3a(3) =12a(4) =57a(5) =300a(6) =1693a(7) =10045a(8) =61890a(9) =392688a(10) =2550843a(11) =16891566a(12) =113660475a(13) =775223595a(14) =5349057132a(15) =37280705406a(16) =262119009927

External references