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A098558
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Expansion of e.g.f. (1+x)/(1-x).
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20
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1, 2, 4, 12, 48, 240, 1440, 10080, 80640, 725760, 7257600, 79833600, 958003200, 12454041600, 174356582400, 2615348736000, 41845579776000, 711374856192000, 12804747411456000, 243290200817664000, 4865804016353280000, 102181884343418880000, 2248001455555215360000
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OFFSET
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0,2
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COMMENTS
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Essentially the same as A052849: a(0)=0 and a(n) = A052849(n) for n>=1.
Also the number of graceful labelings of the star graph on n+1 nodes. - Eric W. Weisstein, Mar 31 2020
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LINKS
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FORMULA
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a(n) = 2*n! - 0^n = 2*n! - !n.
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MATHEMATICA
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With[{nn=30}, CoefficientList[Series[(1+x)/(1-x), {x, 0, nn}], x] Range[0, nn]!] (* Harvey P. Dale, Jun 05 2021 *)
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PROG
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(PARI) concat([1], vector(30, n, 2*n!)) \\ G. C. Greubel, Jan 17 2018
(Magma) [1] cat [2*Factorial(n): n in [1..30]]; // G. C. Greubel, Jan 17 2018
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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