%I #5 Feb 03 2022 10:42:26
%S 1,0,1,6,37,240,1693,13446,122329,1261104,14332681,175123446,
%T 2267871517,30981705984,446571784261,6798161166486,109220619908593,
%U 1846729159654560,32726973173941585,605358657750562470,11648701234354836565,232655173657593759312
%N G.f. A(x) satisfies: A(x) = 1 + x^2 * A(x/(1 - 6*x)) / (1 - 6*x).
%C Shifts 2 places left under 6th-order binomial transform.
%F a(0) = 1, a(1) = 0; a(n) = Sum_{k=0..n-2} binomial(n-2,k) * 6^k * a(n-k-2).
%t nmax = 21; A[_] = 0; Do[A[x_] = 1 + x^2 A[x/(1 - 6 x)]/(1 - 6 x) + O[x]^(nmax + 1) // Normal, nmax + 1]; CoefficientList[A[x], x]
%t a[0] = 1; a[1] = 0; a[n_] := a[n] = Sum[Binomial[n - 2, k] 6^k a[n - k - 2], {k, 0, n - 2}]; Table[a[n], {n, 0, 21}]
%Y Cf. A000994, A005012, A351057, A351143, A351144, A351150, A351151.
%K nonn
%O 0,4
%A _Ilya Gutkovskiy_, Feb 02 2022