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Search: id:A134291
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| 1, 55, 1210, 15730, 143143, 1002001, 5725720, 27810640, 118195220, 449141836, 1551580888, 4936848280, 14620666060, 40648664980, 106847919376, 267119798440, 638337753625, 1464421905375, 3237143159250, 6917263803450
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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See a comment under A134288 on the coincidence of column and diagonal sequences.
Kekul\'e numbers K(O(1,9,n)) for certain benzenoids (see the Cyvin-Gutman reference, p. 105, eq. (i)).
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REFERENCES
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S. J. Cyvin and I. Gutman, Kekul\'e structures in benzenoid hydrocarbons, Lecture Notes in Chemistry, No. 46, Springer, New York, 1988.
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FORMULA
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a(n)= A001263(n+10,10) = binomial(n+10,10)*binomial(n+10,9)/(n+10).
O.g.f.: P(9,x)/(1-x)^19 with the numerator polynomial P(9,x)=sum(A001263(9,k)*x^(k-1),k=1..9), the ninth row polynomial of the Narayana triangle. P(9,x)=1+36*x+336*x^2+1176*x^3+1764*x^4+1176*x^5+336*x^6+36*x^7+x^8.
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CROSSREFS
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Cf. A134290 (ninth column of Narayana triangle).
Sequence in context: A053138 A027784 A008402 this_sequence A017771 A017718 A077688
Adjacent sequences: A134288 A134289 A134290 this_sequence A134292 A134293 A134294
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KEYWORD
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nonn,easy
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de) Nov 13 2007
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