69514domain: NAppears in sequencesa(n) = 3*a(n-1) + a(n-2) + n.at n=9A117917The Wiener index of the graph \|/_\/_\/_..._\/_\|/ having n nodes on the horizontal path.at n=32A180571O.g.f.: exp( Sum_{n>=1} -(sigma(2*n^2) - sigma(n^2)) * (-x)^n/n ).at n=36A215603