A342405 a(n) = (27^n - 3*9^n - 3*12^n)/6 + 6^n.

0, 45, 2268, 76221, 2245320, 62858025, 1723364748, 46836754821, 1268169391440, 34282547074305, 926123262507828, 25011175461289821, 675371104361586360, 18235844869321055385, 492377645105637260508, 13294313813660319607221, 358947876218708733778080

Offset: 1

Author

Petros Hadjicostas, Mar 10 2021

Keywords

• nonn

Links

• Index entries for linear recurrences with constant coefficients, signature (54,-963,6966,-17496).

Crossrefs

Column 3 of A342202.

Formula

From Chai Wah Wu, Mar 11 2021: (Start)

a(n) = 54*a(n-1) - 963*a(n-2) + 6966*a(n-3) - 17496*a(n-4) for n > 4.

G.f.: 9*x^2*(-324*x^2 - 18*x + 5)/((6*x - 1)*(9*x - 1)*(12*x - 1)*(27*x - 1)). (End)

a(n) == 0 (mod 81) for n >= 3. - Hugo Pfoertner, Mar 11 2021