a(n) = [x^((n*(n+1)/2)^2)] Product_{k=1..n} Sum_{m>=0} x^(k^2*m).

A321183

a(n) = [x^((n*(n+1)/2)^2)] Product_{k=1..n} Sum_{m>=0} x^(k^2*m).

Terms

    a(0) =1a(1) =1a(2) =3a(3) =26a(4) =438a(5) =11674a(6) =434613a(7) =21040885a(8) =1263748763a(9) =91057116368

External references