a(n) = 31*binomial(2*n,n-4) + Sum_{i=1..n-4} binomial(2*n,n-4-i)*(4+i).

A182025

a(n) = 31*binomial(2*n,n-4) + Sum_{i=1..n-4} binomial(2*n,n-4-i)*(4+i).

Terms

    a(0) =0a(1) =0a(2) =0a(3) =0a(4) =31a(5) =315a(6) =2112a(7) =11830a(8) =60060a(9) =287028a(10) =1317840a(11) =5883768a(12) =25741485a(13) =110921525a(14) =472431960a(15) =1993896450a(16) =8354335080a(17) =34799391000a(18) =144259293600a(19) =595644532560

External references