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A081132
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(n+1)^n*C(n+2,2).
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3
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1, 6, 54, 640, 9375, 163296, 3294172, 75497472, 1937102445, 55000000000, 1711870023666, 57954652913664, 2120125746145771, 83340051191685120, 3503151123046875000, 156797324626531188736, 7445162356977030877593
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| A diagonal of A081130.
a(n) is the sum of all the fixed points in the set of endofunctions on {1,2,...,n+1} i.e. the functions f:{1,2,...,n+1}->{1,2,...,n+1}. - Geoffrey Critzer Sep 17 2011
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..300
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FORMULA
| a(n)=(n+1)^(n)C(n+2, 2).
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EXAMPLE
| a(1) = 6 because there are four functions from {1,2} into {1,2}: (1*,1) (1*,2*) (2,1) (2,2*) and the fixed points (marked *) sum to 6.
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MATHEMATICA
| Table[n^n (n+1)/2, {n, 1, 16}]
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PROG
| (MAGMA)[((n+1)^n*Binomial(n+2, 2)): n in [0..20]]; // Vincenzo Librandi, Sep 21 2011
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CROSSREFS
| Cf. A081131.
Sequence in context: A201352 A186375 A069726 * A158831 A034001 A084062
Adjacent sequences: A081129 A081130 A081131 * A081133 A081134 A081135
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), Mar 08 2003
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