A131298 Diagonal sums of A104730.

1, 1, 2, 4, 6, 11, 18, 30, 50, 82, 135, 221, 361, 589, 959, 1560, 2535, 4116, 6679, 10832, 17560, 28457, 46103, 74674, 120928, 195802, 316995, 513148, 830608, 1344372, 2175796, 3521249, 5698477

Offset

0,3

Links

Table of n, a(n) for n=0..32.

Index entries for linear recurrences with constant coefficients, signature (1,2,0,-2,-1).

Formula

G.f.: (1-x^2)/((1-x-x^2)*(1-x^2-x^3)) = (1+x)/(1-x-x^2) - x*(1+x)/(1-x^2-x^3).

a(n) = Sum_{k=0..floor(n/2)} C(n-k+1,k) - C(k,n-2k+1).

Mathematica

LinearRecurrence[{1, 2, 0, -2, -1}, {1, 1, 2, 4, 6}, 40] (* Harvey P. Dale, Aug 21 2021 *)

Crossrefs

Cf. A104730.

Sequence in context: A026636 A026658 A138688 * A168445 A328669 A185192

Adjacent sequences: A131295 A131296 A131297 * A131299 A131300 A131301

Keyword

easy,nonn

Author

Paul Barry, Jun 26 2007

Status

approved