A106469 Expansion of (1 + x^2)*(1 + 2*x)/(1 - x^2).

1, 2, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4, 2, 4

Offset

0,2

Links

Table of n, a(n) for n=0..95.

Index entries for linear recurrences with constant coefficients, signature (0,1).

Formula

a(0)=1, a(n)=(2-0^((n-1)/2))(1-(-1)^n)+(2-0^(n/2))(1+(-1)^n)/2, n>1.

Mathematica

CoefficientList[Series[(1+x^2)(1+2x)/(1-x^2), {x, 0, 95}], x] (* James C. McMahon, Feb 02 2024 *)

Crossrefs

Row sums of A106468.

Sequence in context: A100374 A045841 A040003 * A082508 A327730 A365348

Adjacent sequences: A106466 A106467 A106468 * A106470 A106471 A106472

Keyword

easy,nonn

Author

Paul Barry, May 03 2005

Status

approved