81768domain: NAppears in sequencesa(n) = T(2n,n-1), where T is the array in A026148.at n=7A026160Triangle read by rows: T(n,k) = number of Ringel ladders of order n and genus k.at n=40A298800Expansion of e.g.f. Sum_{k>0} x^k / ((k-1)! - x^k).at n=7A358594Numbers k such that k + sopfr(k) is a cube.at n=40A389862