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A111587 a(n) = 2*a(n-1) + 2*a(n-3) + a(n-4), a(0) = 1, a(1) = 4, a(2) = 9, a(3) = 20. 0
1, 4, 9, 20, 49, 120, 289, 696, 1681, 4060, 9801, 23660, 57121, 137904, 332929, 803760, 1940449, 4684660, 11309769, 27304196, 65918161, 159140520, 384199201, 927538920, 2239277041, 5406093004, 13051463049, 31509019100, 76069501249 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..28.

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

FORMULA

a(2n) = A090390(n+1), a(2n+1) = A046729(n+1); G.f. (x+1)^2/((x^2+1)*(1-2*x-x^2)).

a(n) = A057077(n+1)/2 - A001333(n+2)/2. [R. J. Mathar, Nov 10 2009]

MATHEMATICA

LinearRecurrence[{2, 0, 2, 1}, {1, 4, 9, 20}, 30] (* Harvey P. Dale, Jul 26 2011 *)

PROG

Floretion Algebra Multiplication Program, FAMP Code: 2kbasekseq[J+G] with J = + j' + k' + 'ii' and G = + .5'ii' + .5'jj' + .5'kk' + .5e

CROSSREFS

Cf. A090390, A046729, A111588, A019898.

Sequence in context: A144685 A109110 A108870 * A161221 A130045 A225986

Adjacent sequences:  A111584 A111585 A111586 * A111588 A111589 A111590

KEYWORD

easy,nonn

AUTHOR

Creighton Dement, Aug 08 2005

EXTENSIONS

Flipped sign of the generating function - R. J. Mathar, Nov 10 2009

STATUS

approved

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Last modified August 21 13:36 EDT 2017. Contains 290890 sequences.