

A135360


a(n) = 4*a(n1)  6*a(n2) + 4*a(n3) for n > 4, with first terms 1, 2, 4, 7.


1



1, 2, 4, 7, 12, 22, 44, 92, 192, 392, 784, 1552, 3072, 6112, 12224, 24512, 49152, 98432, 196864, 393472, 786432, 1572352, 3144704, 6290432, 12582912, 25167872, 50335744, 100667392, 201326592, 402644992, 805289984, 1610596352, 3221225472, 6442483712, 12884967424
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OFFSET

0,2


COMMENTS

Sequence identical to its fourth differences.
Without a(3)=7, sequence A000079 would have been obtained.  Michel Marcus, May 06 2015


LINKS

G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (4,6,4).


FORMULA

a(n) = 2^n + A000749(n).  Michel Marcus, May 06 2015
G.f.: (1  x)*(1  x + x^2)/((1  2*x)*(1  2*x + 2*x^2)). [Bruno Berselli, May 06 2015]


MATHEMATICA

Join[{1}, LinearRecurrence[{4, 6, 4}, {2, 4, 7}, 25]] (* G. C. Greubel, Oct 11 2016 *)


PROG

(PARI) lista(nn) = {v = vector(nn); v[1] = 1; v[2] = 2; v[3] = 4; v[4] = 7; for (k=5, nn, v[k] = 4*v[k1]6*v[k2]+4*v[k3]; ); v; } \\ Michel Marcus, May 06 2015


CROSSREFS

Cf. A000079 (2^n), A000749.
Sequence in context: A023432 A072641 A280352 * A082548 A270995 A299023
Adjacent sequences: A135357 A135358 A135359 * A135361 A135362 A135363


KEYWORD

nonn,easy


AUTHOR

Paul Curtz, Dec 08 2007


EXTENSIONS

More terms from Michel Marcus, May 06 2015


STATUS

approved



