99826domain: NAppears in sequencesCoefficient of x^4 in expansion of (1+x+x^2)^n.at n=36A005712Number of binary strings of length n with no substrings equal to 0011 0101 or 1010.at n=20A164504a(n) = trinomial(2*n, 4) = (1/6)*n*(2*n - 1)*(2*n^2 + 7*n - 3).at n=19A302710