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A278565 a(n) = Sum_{t=1..n} binomial(n,t)*t^(1+(n-t)^2). 0
0, 1, 4, 18, 236, 12760, 3162582, 5965957900, 147395915019656, 38431930179989653632, 90116582088416163834417290, 2118032070086776060232851050813004, 966490912699216393489571072350268614425420, 17165261065730992639912668446254005264689353839299152 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Table of n, a(n) for n=0..13.

Daniel J. Kleitman, Bruce L. Rothschild and Joel H. Spencer, The number of semigroups of order n, Proc. Amer. Math. Soc., 55 (1976), 227-232. See Eq. (1.2).

MATHEMATICA

Table[Sum[Binomial[n, t]  t^(1 + (n - t)^2), {t, 1, n}], {n, 0, 25}] (* Vincenzo Librandi, Nov 27 2016 *)

CROSSREFS

Cf. A001423.

Sequence in context: A143993 A145660 A246531 * A214168 A214189 A214240

Adjacent sequences:  A278562 A278563 A278564 * A278566 A278567 A278568

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Nov 25 2016

STATUS

approved

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Last modified June 17 00:17 EDT 2021. Contains 345080 sequences. (Running on oeis4.)