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A099624 Sum C(n-k,k+2)3^(n-k-2)(4/3)^k, k=0..floor(n/2). 1
0, 0, 1, 9, 58, 318, 1591, 7503, 33976, 149436, 643261, 2724357, 11395654, 47210154, 194121811, 793526571, 3228811492, 13090123272, 52917410041, 213437246145, 859342367890, 3455021317590, 13875655896751, 55677180731079 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

In general a(n)=sum{k=0..floor(n/2), C(n-k,k+2)u^(n-k-2)(v/u)^k has g.f. x^2/((1-u*x)^2(1-u*x-v*x^2)) and satisfies the recurrence a(n)=3u*a(n-1)-(3u^2-v)a(n-2)+(u^3-2uv)a(n-3)+u^2^v*a(n-4).

LINKS

Table of n, a(n) for n=0..23.

Index entries for linear recurrences with constant coefficients, signature (9,-23,3,36).

FORMULA

G.f.: x^2/((1-3x)^2(1-3x-4x^2)); a(n)=9a(n-1)-23a(n-2)+3a(n-3)+36a(n-4).

CROSSREFS

Cf. A099623.

Sequence in context: A044528 A027174 A304370 * A018218 A026750 A009034

Adjacent sequences:  A099621 A099622 A099623 * A099625 A099626 A099627

KEYWORD

easy,nonn

AUTHOR

Paul Barry, Oct 25 2004

STATUS

approved

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Last modified August 11 03:41 EDT 2022. Contains 356046 sequences. (Running on oeis4.)