a(n) = Sum_{k=1..n} binomial(2*n, k) * sigma_2(k).

Terms

a(0) =2a(1) =34a(2) =281a(3) =2178a(4) =12397a(5) =79729a(6) =398932a(7) =2224354a(8) =10959221a(9) =56341309a(10) =255685080a(11) =1334248401a(12) =5892916876a(13) =28082515768a(14) =127714609741a(15) =604178948098