A019485 a(n) = 2*a(n-1) + 2*a(n-2) - 3*a(n-3).

2, 5, 12, 28, 65, 150, 346, 797, 1836, 4228, 9737, 22422, 51634, 118901, 273804, 630508, 1451921, 3343446, 7699210, 17729549, 40827180, 94015828, 216497369, 498544854, 1148036962, 2643671525, 6087782412, 14018796988, 32282144225, 74338535190, 171184967866

Offset

0,1

References

R. K. Guy, personal communication.

Links

Table of n, a(n) for n=0..30.

Index entries for linear recurrences with constant coefficients, signature (2,2,-3).

Formula

G.f.: ( 2+x-2*x^2 ) / ( (x-1)*(3*x^2+x-1) ). - R. J. Mathar, Feb 11 2016

Mathematica

LinearRecurrence[{2, 2, -3}, {2, 5, 12}, 50] (* Harvey P. Dale, Jan 19 2021 *)

Prog

(Magma) I:=[2, 5, 12]; [n le 3 select I[n] else 2*Self(n-1) + 2*Self(n-2) - 3*Self(n-3): n in [1..30]]; // Wesley Ivan Hurt, Dec 27 2021

Crossrefs

Cf. A018914.

Sequence in context: A001410 A258898 A019486 * A018914 A129519 A034943

Adjacent sequences: A019482 A019483 A019484 * A019486 A019487 A019488

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved