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A000535
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Card matching.
(Formerly M5194 N2258)
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2
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0, 27, 378, 4536, 48600, 489780, 4738104, 44535456, 409752432, 3708359550, 33125746500, 292779558720, 2565087894720, 22307854940280, 192788833482000, 1657111548654720, 14176605442521312, 120779466450505758
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Number of permutations of 3 distinct letters (ABC) each with n copies such that two (2) fixed points. E.g. if AAAAABBBBBCCCCC n=3*5 letters permutations then two fixed points n5=48600 - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Feb 02 2006
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REFERENCES
| J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 193.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Index entries for sequences related to card matching
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FORMULA
| a(n)=3binomial(n, 2)*sum(binomial(n, k+2)*binomial(n, k)*binomial(n-2, k), k=0..n-2) + 3n^2*sum(binomial(n, k+1)*binomial(n-1, k+1)*binomial(n-1, k), k=0..n-2).
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CROSSREFS
| Cf. A000279, A000489.
Cf. A033581.
Sequence in context: A162726 A010979 A022591 * A033280 A125462 A036222
Adjacent sequences: A000532 A000533 A000534 * A000536 A000537 A000538
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 26 2000
More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Feb 19 2004
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