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Search: id:A001247
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| A001247 |
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Squares of Bell numbers. |
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+0
2
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| 1, 1, 4, 25, 225, 2704, 41209, 769129, 17139600, 447195609, 13450200625, 460457244900, 17754399678409, 764214897046969, 36442551140059684, 1912574337188517025, 109833379421325769609, 6866586647633870998416
(list; graph; listen)
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OFFSET
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0,3
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FORMULA
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E.g.f.: exp(exp(x*(d_z) - 1))*(exp(exp(z)-1)) |_{z=0}, with the derivative operator d_z := d/dz. From eqs.(16) and (17) of the 1999 C. M. Bender reference given in A000110.
E.g.f.: exp(-2)*Sum(exp(exp(n*x))/n!,n=0..infinity). - Vladeta Jovovic (vladeta(AT)Eunet.yu), Jan 31 2008
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MAPLE
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with (combinat):seq(mul(bell(n), k=1..2), n=0..17); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Sep 21 2007
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CROSSREFS
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Cf. A000110.
Sequence in context: A060911 A060912 A050386 this_sequence A031152 A010845 A087660
Adjacent sequences: A001244 A001245 A001246 this_sequence A001248 A001249 A001250
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KEYWORD
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nonn,easy
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AUTHOR
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njas
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EXTENSIONS
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More terms from Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Sep 21 2007
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