446216domain: NAppears in sequencesa(n) = (1/3)*(n^2 + 2*n + 3)*(n+1)^2.at n=33A014820Numbers k that divide 6^k + 2^k.at n=43A045579Octagonal numbers equal to S*(3S - 2) with 3S - 2 = k^2 and S semiprime.at n=13A124106Octagonal numbers of the form C*(3C - 2) with 3C - 2 = k^2 and C a composite number.at n=16A125511