A115851 G.f. x^2*(-1+x+x^2)/((1-x)*(2*x-1)*(x+1)*(x^2+1)).

0, 0, 1, 1, 1, 2, 5, 9, 17, 34, 69, 137, 273, 546, 1093, 2185, 4369, 8738, 17477, 34953, 69905, 139810, 279621, 559241, 1118481, 2236962, 4473925, 8947849, 17895697, 35791394, 71582789, 143165577, 286331153, 572662306, 1145324613

Offset

0,6

Links

Table of n, a(n) for n=0..34.

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

Formula

a(n) + a(n+2) = A005578(n).

a(n) = (2^n - 1)/15 if n == 0 (mod 4), (2^n - 2)/15 if n == 1 (mod 4), (2^n + 11)/15 if n == 2 (mod 4), (2^n + 7)/15 if n == 3 (mod 4). - Robert Israel, Mar 14 2023

Maple

B:= [-1, -2, 11, 7]:
seq((2^n + B[(n mod 4)+1])/15, n=0..50); # Robert Israel, Mar 14 2023

Crossrefs

Cf. A005578, A001045.

Sequence in context: A292168 A322304 A182992 * A163734 A336141 A184353

Adjacent sequences: A115848 A115849 A115850 * A115852 A115853 A115854

Keyword

nonn,easy

Author

Creighton Dement, Mar 29 2006

Status

approved