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A296944
Expansion of (2*x*exp(x)-3)/(1-x).
2
0, 1, 2, 12, 56, 290, 1752, 12278, 98240, 884178, 8841800, 97259822, 1167117888, 15172532570, 212415456008, 3186231840150, 50979709442432, 866655060521378, 15599791089384840, 296396030698311998, 5927920613966240000, 124486332893291040042
OFFSET
0,3
COMMENTS
Number of bisymmetric and quasitrivial binary operations on {1,...,n} that have annihilator elements.
LINKS
FORMULA
a(n) = A296943(n)-2, a(0) = 0, a(1) = 1.
MATHEMATICA
Join[{0, 1}, Delete[ Range[0, 21]! CoefficientList[ Series[(2x*Exp[x] -3)/(1 -x), {x, 0, 21}], x], {{1}, {2}}]] (* Robert G. Wilson v, Dec 22 2017 *)
CROSSREFS
Cf. A296943.
Sequence in context: A078543 A084128 A044047 * A105487 A098453 A256150
KEYWORD
nonn,easy
AUTHOR
J. Devillet, Dec 22 2017
STATUS
approved