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A108678 a(n) = (n+1)^2*(n+2)(2n+3)/6. 1
1, 10, 42, 120, 275, 546, 980, 1632, 2565, 3850, 5566, 7800, 10647, 14210, 18600, 23936, 30345, 37962, 46930, 57400, 69531, 83490, 99452, 117600, 138125, 161226, 187110, 215992, 248095, 283650, 322896, 366080, 413457, 465290, 521850, 583416, 650275, 722722 (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. 232, # 44).

LINKS

Table of n, a(n) for n=0..37.

FORMULA

G.f.: (1 + 5*x + 2*x^2)/(1-x)^5.

a(n) = A098077(n+1)/2. - Alexander Adamchuk, Apr 12 2006

MAPLE

a:=n->(n+1)^2*(n+2)*(2*n+3)/6: seq(a(n), n=0..42);

a:=n->sum(n*j^2, j=1..n): seq(a(n), n=1..36); # Zerinvary Lajos, Apr 29 2007

MATHEMATICA

Table[(n+1)^2*(n+2)(2n+3)/6, {n, 0, 100}] (* Vladimir Joseph Stephan Orlovsky, Jun 03 2011 *)

CROSSREFS

Cf. A098077.

Sequence in context: A086544 A031146 A163815 * A226988 A027171 A003822

Adjacent sequences:  A108675 A108676 A108677 * A108679 A108680 A108681

KEYWORD

nonn,easy

AUTHOR

Emeric Deutsch, Jun 17 2005

STATUS

approved

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Last modified May 27 22:57 EDT 2017. Contains 287210 sequences.