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A290597
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Numerators in the expansion of the exponential generating function ((1 + 3*x)/x)*(1 - (1 + 3*x)^(-2/3)).
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7
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2, 1, -10, 20, -176, 6160, -29920, 523600, -96342400, 250490240, -6603833600, 581137356800, -6258402304000, 220832195584000, -25351536053043200, 348583620729344000, -15419698987556864000, 6553372069711667200000, -36560917862601932800000, 1945040830290422824960000, -327878311391814133350400000, 6468144870183969721548800000, -402149876711438117470208000000, 78620300897086151965425664000000, -1786253236381797372654471086080000, 127098787973320197669645058048000000
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OFFSET
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0,1
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COMMENTS
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The denominators are A038500(n+1), n >= 0.
The rationals z(n) = a(n)/A038500(n+1) give the Sheffer z-sequence for the generalized unsigned Lah triangle L[3,1] = A290596. For Sheffer a- and z-sequences see a W. Lang link under A006232 with the references for the Riordan case, and also the present link for a proof.
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LINKS
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FORMULA
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a(n) = numerator(r(n)) with the rationals r(n) = [x^n/n!] ((1 + 3*x)/x)*(1 - (1 + 3*x)^(-2/3)).
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EXAMPLE
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The rationals r(n) = z(3,1;n) = a(n)/A038500(n+1) begin: {2, 1, -10/3, 20, -176, 6160/3, -29920, 523600, -96342400/9, 250490240, -6603833600, 581137356800/3, -6258402304000, 220832195584000, -25351536053043200/3, 348583620729344000, ...}.
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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