a(1) = 2; for n >= 2, a(n) = f(a(n-1)) where f(n) = n*(n+1)*(n+2)*(n+3)/24.

A100009

a(1) = 2; for n >= 2, a(n) = f(a(n-1)) where f(n) = n*(n+1)*(n+2)*(n+3)/24.

Terms

    a(0) =2a(1) =5a(2) =70a(3) =1088430

External references