11174374domain: NAppears in sequencesSequence equals its 4th differences shifted by one index.at n=20A137166a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) + a(n-4) with a(1) = 1, a(2) = 2, a(3) = 4, and a(4) = 7.at n=27A385106