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Search: id:A006230
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| A006230 |
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Bitriangular permutations.
(Formerly M4902)
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+0
1
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| 1, 13, 73, 301, 1081, 3613, 11593, 36301, 111961, 342013, 1038313, 3139501, 9467641, 28501213, 85700233, 257493901, 773268121, 2321377213, 6967277353, 20908123501
(list; graph; listen)
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OFFSET
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4,2
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
I. Kaplansky and J. Riordan, The problem of the rooks and its applications, Duke Math. J., 13 (1946), 259-268.
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LINKS
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S. Plouffe, Approximations de S\'{e}ries G\'{e}n\'{e}ratrices et Quelques Conjectures, Dissertation, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
S. Plouffe, 1031 Generating Functions and Conjectures, Universit\'{e} du Qu\'{e}bec \`{a} Montr\'{e}al, 1992.
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FORMULA
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a(n) = 12*S(n-2) + 1, with S(n)=A000392(n) the Stirling numbers of second kind. - Ralf Stephan (ralf(AT)ark.in-berlin.de), Jul 07 2003
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MAPLE
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A006230:=-(z+1)*(6*z+1)/(z-1)/(3*z-1)/(2*z-1); [Conjectured by S. Plouffe in his 1992 dissertation.]
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CROSSREFS
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Sequence in context: A081586 A143008 A107963 this_sequence A066110 A020527 A146618
Adjacent sequences: A006227 A006228 A006229 this_sequence A006231 A006232 A006233
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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