A125691 Expansion of 1/(1 - x - 3x^2 + x^3).

1, 1, 4, 6, 17, 31, 76, 152, 349, 729, 1624, 3462, 7605, 16367, 35720, 77216, 168009, 363937, 790748, 1714550, 3722857, 8075759, 17529780, 38034200, 82547781, 179120601, 388729744, 843543766, 1830612397, 3972513951, 8620807376, 18707736832, 40597645009, 88100048129

Offset: 0

Author

Paul Barry, Nov 30 2006

Keywords

• easy
• nonn

Comments

Antidiagonal sums of number triangle A125690.

Links

• Indranil Ghosh, Table of n, a(n) for n = 0..200
• Index entries for linear recurrences with constant coefficients, signature (1,3,-1).

Crossrefs

Cf. A125690.

Programs

Mathematica

CoefficientList[Series[1/(1 - x - 3x^2 + x^3), {x, 0, 28}], x] (* Indranil Ghosh, Mar 10 2017 *)
LinearRecurrence[{1,3,-1},{1,1,4},40] (* Harvey P. Dale, Jul 13 2019 *)

PARI

Vec(1/(1 - x - 3*x^2 + x^3) + O(x^29)) \\ Indranil Ghosh, Mar 10 2017