44915domain: NAppears in sequencesa(n) = number of 7-digit primes with digit sum n, where n runs through the non-multiples of 3 in the range [2..62].at n=20A178876a(n) = n*F(n+1) - (n+1)*F(n), where F = A000045.at n=19A264147a(n) = [x^n] 1/(1 + x + x^2 + x^3)^n.at n=12A350406