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A107963 a(n) = (n+1)*(n+2)*(n+3)*(n+4)*(5*n^2 + 19*n + 15)/360. 5
1, 13, 73, 273, 798, 1974, 4326, 8646, 16071, 28171, 47047, 75439, 116844, 175644, 257244, 368220, 516477, 711417, 964117, 1287517, 1696618, 2208690, 2843490, 3623490, 4574115, 5723991, 7105203, 8753563, 10708888, 13015288, 15721464 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
Kekulé numbers for certain benzenoids.
REFERENCES
S. J. Cyvin and I. Gutman, Kekulé structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 229).
LINKS
FORMULA
G.f.: ( -1-6*x-3*x^2 ) / (x-1)^7 . - R. J. Mathar, Feb 16 2011
a(n) = Sum_{i=0..n+1} A000217(i)*A000292(i) with a(-1)=0. - Bruno Berselli, Jul 20 2015
MAPLE
a:=n->(1/360)*(n+1)*(n+2)*(n+3)*(n+4)*(5*n^2+19*n+15): seq(a(n), n=0..36);
MATHEMATICA
LinearRecurrence[{7, -21, 35, -35, 21, -7, 1}, {1, 13, 73, 273, 798, 1974, 4326}, 40] (* Vincenzo Librandi, Apr 23 2017 *)
PROG
(PARI) a(n)=(n+1)*(n+2)*(n+3)*(n+4)*(5*n^2+19*n+15)/360 \\ Charles R Greathouse IV, Oct 16 2015
(Magma) [(n+1)*(n+2)*(n+3)*(n+4)*(5*n^2+19*n+15)/360: n in [0..30]]; // Vincenzo Librandi, Apr 23 2017
CROSSREFS
Equals third right hand column of A161739 (RSEG2 triangle). - Johannes W. Meijer, Jun 18 2009
Sequence in context: A060886 A081586 A143008 * A006230 A066110 A020527
KEYWORD
nonn,easy
AUTHOR
Emeric Deutsch, Jun 12 2005
STATUS
approved

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Last modified March 28 13:42 EDT 2024. Contains 371254 sequences. (Running on oeis4.)