This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A108646 a(n) = (n+1)(n+2)^2*(n+3)(11n^3 + 58n^2 + 101n + 60)/720. 1
 1, 23, 194, 985, 3668, 11074, 28728, 66438, 140415, 276001, 511082, 900263, 1519882, 2473940, 3901024, 5982300, 8950653, 13101051, 18802210, 26509637, 36780128, 50287798, 67841720, 90405250, 119117115, 155314341, 200557098 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS KekulĂ© numbers for certain benzenoids. REFERENCES S. J. Cyvin and I. Gutman, KekulĂ© structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988 (p. 230, no. 22). LINKS Chai Wah Wu, Table of n, a(n) for n = 0..10000 FORMULA From Chai Wah Wu, Jun 12 2016: (Start) a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n > 7. G.f.: (2*x^4 + 21*x^3 + 38*x^2 + 15*x + 1)/(x - 1)^8. (End) MAPLE a:=(n+1)*(n+2)^2*(n+3)*(11*n^3+58*n^2+101*n+60)/720: seq(a(n), n=0..30); PROG (Python) A108646_list, m = [], [77, -85, 28, -1, 1, 1, 1, 1] for _ in range(10001):     A108646_list.append(m[-1])     for i in range(7):         m[i+1] += m[i] # Chai Wah Wu, Jun 12 2016 CROSSREFS Sequence in context: A160083 A140545 A062640 * A307355 A058193 A065314 Adjacent sequences:  A108643 A108644 A108645 * A108647 A108648 A108649 KEYWORD nonn AUTHOR Emeric Deutsch, Jun 13 2005 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified July 23 15:55 EDT 2019. Contains 325258 sequences. (Running on oeis4.)