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1, 4, 22, 154, 1306, 12994, 148282, 1908274, 27333706, 431220034, 7428550042, 138737478994, 2792050329706, 60231133487074, 1386484468239802, 33921605427779314, 878976357571495306, 24046780495646314114, 692622345890928153562, 20950628198687114521234, 663992311200423614606506
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Stirling transform of A052849(n+1)=[4,12,48,240,...] is 4*a(n)=[4,16,88,616,...]. - Michael Somos Mar 04 2004
Stirling transform of A001710(n+1)=[1,3,12,160,...] is a(n)=[1,4,22,154,...]. - Michael Somos Mar 04 2004
Stirling transform of A001563(n+1)=[4,18,96,600,...] is a(n+1)=[4,22,154,...]. - Michael Somos Mar 04 2004
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LINKS
| N. J. A. Sloane and Thomas Wieder, The Number of Hierarchical Orderings, Order 21 (2004), 83-89.
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FORMULA
| E.g.f.: (1/(2-exp(x))^2-1)/2. - Michael Somos Mar 04 2004
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PROG
| (PARI) a(n)=if(n<0, 0, n!*polcoeff(subst((1/(1-y)^2-1)/2, y, exp(x+x*O(x^n))-1), n))
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CROSSREFS
| A005649(n)=2*a(n), if n>0.
Pairwise sums of A091346.
Sequence in context: A196275 A000307 A049376 * A052772 A052650 A198053
Adjacent sequences: A083407 A083408 A083409 * A083411 A083412 A083413
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jun 08 2003
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