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 A212599 Number of functions on n labeled points to themselves (endofunctions) such that the number of cycles of f that have each even size is even. 3
 1, 1, 3, 18, 160, 1875, 27126, 466186, 9275064, 209654325, 5307031000, 148720701426, 4570816040352, 152874605142727, 5527634477245440, 214862754390554250, 8934811701563214976, 395788795274021394729, 18606559519007667893376, 925222631836457779380370, 48518852386696450625510400 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..200 FORMULA E.g.f.: ((1+T(x))/(1-T(x)))^(1/2) * Product_{i>=1} cosh(T(x)^(2*i)/(2*i)) where T(x) is the e.g.f. for A000169. MAPLE with(combinat): b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,       add(`if`(irem(j, igcd(i, 2))<>0, 0, (i-1)!^j*       multinomial(n, n-i*j, i\$j)/j!*b(n-i*j, i-1)), j=0..n/i)))     end: a:= n-> add(b(j, j)*n^(n-j)*binomial(n-1, j-1), j=0..n): seq(a(n), n=0..25);  # Alois P. Heinz, Sep 08 2014 MATHEMATICA nn=20; t=Sum[n^(n-1)x^n/n!, {n, 1, nn}]; p=Product[Cosh[t^(2i)/(2i)], {i, 1, nn}]; Range[0, nn]! CoefficientList[Series[((1+t)/(1-t))^(1/2) p, {x, 0, nn}], x] CROSSREFS Cf. A003483, A246951, A116956. Sequence in context: A352638 A238302 A067302 * A052182 A309985 A328030 Adjacent sequences:  A212596 A212597 A212598 * A212600 A212601 A212602 KEYWORD nonn,nice AUTHOR Geoffrey Critzer, May 22 2012 EXTENSIONS Maple program fixed by Vaclav Kotesovec, Sep 13 2014 STATUS approved

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Last modified May 19 23:40 EDT 2022. Contains 353847 sequences. (Running on oeis4.)