98068domain: NAppears in sequencesa(n) = Sum_{i=0..n} digsum_9(i)^4, where digsum_9(i) = A053830(i).at n=40A231687Solution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n-1) + 2n, where a(0) = 1, a(1) = 2, b(0) = 3, and (a(n)) and (b(n)) are increasing complementary sequences.at n=19A294547