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 A033462 Exponential (or "EXP") transform of squares A000290. 12
 1, 1, 5, 22, 125, 836, 6277, 52396, 479593, 4757680, 50738921, 577894604, 6990138685, 89376020800, 1203182518189, 16995248375116, 251135780602193, 3871961504546624, 62141329025501905, 1035979079450355532, 17907209511611407141, 320387246623657457056, 5924125441456047522005 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS a(n) is the number of ways to select an ordered pair from each equivalence class in each equivalence relation on {1,2,...,n}. - Geoffrey Critzer, Oct 03 2011 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..500 FORMULA E.g.f.: exp(exp(x)*(x+x^2)). MAPLE a:= proc(n) option remember; `if`(n=0, 1,       add(binomial(n-1, j-1)*j^2*a(n-j), j=1..n))     end: seq(a(n), n=0..25);  # Alois P. Heinz, Mar 30 2016 MATHEMATICA Range[0, 20]! CoefficientList[Series[Exp[Exp[x](x+x^2)], {x, 0, 20}], x] Table[Sum[BellY[n, k, Range[n]^2], {k, 0, n}], {n, 0, 20}] (* Vladimir Reshetnikov, Nov 09 2016 *) PROG (PARI) N=33;  x='x+O('x^N); egf=exp(x*(1+x)*exp(x)); Vec(serlaplace(egf)) /* Joerg Arndt, Sep 15 2012 */ CROSSREFS Column k=2 of A279636. Sequence in context: A020077 A265998 A203265 * A111154 A221539 A028561 Adjacent sequences:  A033459 A033460 A033461 * A033463 A033464 A033465 KEYWORD nonn AUTHOR STATUS approved

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Last modified September 20 17:47 EDT 2020. Contains 337265 sequences. (Running on oeis4.)