A115102 - OEIS

A115102

a(0)=2, a(1)=8, a(n) = a(n-1) + 2*a(n-2).

2, 8, 12, 28, 52, 108, 212, 428, 852, 1708, 3412, 6828, 13652, 27308, 54612, 109228, 218452, 436908, 873812, 1747628, 3495252, 6990508, 13981012, 27962028, 55924052, 111848108, 223696212, 447392428, 894784852, 1789569708, 3579139412, 7158278828

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OFFSET

0,1

COMMENTS

Essentially 2 * A084214.

LINKS

Table of n, a(n) for n=0..31.

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

FORMULA

From R. J. Mathar, Jun 14 2011: (Start)

G.f.: (2+6*x)/( (1+x)*(1-2*x) ).

a(n) = 2*A084214(n+1). (End)

a(n) = (4*(-1)^n + 5*2^n)/3. - Harvey P. Dale, Sep 02 2016

a(n) = 2*a(n-1) - 4*(-1)^n. - Paul Curtz, May 26 2024

MATHEMATICA

LinearRecurrence[{1, 2}, {2, 8}, 40] (* or *) Table[(4(-1)^x+5*2^x)/3, {x, 40}] (* Harvey P. Dale, Sep 02 2016 *)

CROSSREFS

Cf. A078008, A014551.

Cf. A010709.

Sequence in context: A107755 A268836 A027718 * A257082 A265736 A047174

Adjacent sequences: A115099 A115100 A115101 * A115103 A115104 A115105

KEYWORD

nonn,easy

AUTHOR

Roger L. Bagula, Mar 02 2006

EXTENSIONS

Edited by N. J. A. Sloane, Dec 04 2006

STATUS

approved