A274638 Main diagonal of A274637.

0, 0, 3, 5, 15, 27, 63, 119, 255, 495, 1023, 2015, 4095, 8127, 16383, 32639, 65535, 130815, 262143, 523775, 1048575, 2096127, 4194303, 8386559, 16777215, 33550335, 67108863, 134209535, 268435455, 536854527, 1073741823, 2147450879, 4294967295, 8589869055, 17179869183, 34359607295, 68719476735

Offset

0,3

Links

Colin Barker, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (3,0,-6,4).

Formula

From Colin Barker, Jul 09 2016: (Start)

a(n) = (-1+2^n+2^((n-3)/2)*(-1+(-1)^n)).

a(n) = 2^n-1 for n even.

a(n) = 2^n-1-2^((n-1)/2) for n odd.

a(n) = 3*a(n-1)-6*a(n-3)+4*a(n-4) for n>3.

G.f.: x^2*(3-4*x) / ((1-x)*(1-2*x)*(1-2*x^2)).

(End)

Prog

(PARI) concat([0, 0], Vec(x^2*(3-4*x)/((1-x)*(1-2*x)*(1-2*x^2)) + O(x^40))) \\ Colin Barker, Jul 09 2016

Crossrefs

Cf. A274637.

Sequence in context: A289044 A289881 A290230 * A146244 A146457 A051044

Adjacent sequences: A274635 A274636 A274637 * A274639 A274640 A274641

Keyword

nonn,easy

Author

N. J. A. Sloane, Jul 08 2016

Status

approved