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A226223 The number of endomorphisms of the full transformation monoid on the set {1..n}. 2
1, 7, 40, 345, 3226, 38503, 529614, 8219025, 141633028, 2677676931, 55021969234, 1219667932585, 28986449652564, 734758590703803, 19777243624646566, 563105619051710817, 16902630001714260832, 533291777845757001523, 17638752528002502032130, 610137644831701323189321 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..100

B. M. Schein and B. Teclezghi, Endomorphisms of finite full transformation semigroups, Proc. Amer. Math. Soc., 126 (1998) 2579-2587.

PROG

(PARI) a(n)=if(n<5, return([1, 7, 40, 345][n])); n!*(sum(m=1, n, m^(n-m)*sum(k=0, (m-1)\2, sum(r=1, m-2*k, r^(m-k-r)/(m-2*k-r)!/r!)/2^k/k!)/(n-m)!)+1) \\ Charles R Greathouse IV, May 31 2013

CROSSREFS

Cf. A000312.

Sequence in context: A154968 A121582 A239989 * A062727 A223416 A165397

Adjacent sequences:  A226220 A226221 A226222 * A226224 A226225 A226226

KEYWORD

nonn

AUTHOR

James Mitchell, May 31 2013

EXTENSIONS

a(10)-a(20) from Charles R Greathouse IV, May 31 2013

STATUS

approved

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Last modified September 22 09:45 EDT 2017. Contains 292337 sequences.