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 A052686 E.g.f. x^2*(1+3x-3x^2)/(1-x). 0
 0, 0, 2, 24, 24, 120, 720, 5040, 40320, 362880, 3628800, 39916800, 479001600, 6227020800, 87178291200, 1307674368000, 20922789888000, 355687428096000, 6402373705728000, 121645100408832000, 2432902008176640000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 634 FORMULA E.g.f.: x^2*(-3*x+3*x^2-1)/(-1+x) Recurrence: {a(1)=0, a(0)=0, (-1-n)*a(n)+a(n+1)=0, a(2)=2, a(4)=24, a(3)=24} n!, n>3. MAPLE spec := [S, {S=Prod(Z, Z, Union(Z, Z, Z, Sequence(Z)))}, labeled]: seq(combstruct[count](spec, size=n), n=0..20); CROSSREFS Sequence in context: A220773 A055535 A072217 * A064818 A022374 A139334 Adjacent sequences:  A052683 A052684 A052685 * A052687 A052688 A052689 KEYWORD easy,nonn AUTHOR encyclopedia(AT)pommard.inria.fr, Jan 25 2000 STATUS approved

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