63078domain: NAppears in sequencesSolution of the complementary equation a(n) = a(n-1) + a(n-2) + b(n), where a(0) = 2, a(1) = 3, b(0) = 1, b(1) = 4, b(2) = 5, and (a(n)) and (b(n)) are increasing complementary sequences.at n=19A295951a(n) = 1*2*3*4 + 5*6*7*8 + 9*10*11*12 + 13*14*15*16 + 17*18*19*20 + ... + (up to n).at n=18A319205