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A152256
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a(n) = (3^n - 1)*(3^n + 1)^2/32.
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1
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0, 1, 25, 637, 16810, 450241, 12123475, 327035437, 8827268020, 238312027681, 6434206838125, 173721623357437, 4690466178937630, 126642427965100321, 3419344125259375975, 92322278513810982637, 2492701404059145489640, 67302936867273104276161
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = (3^n - 1)*(3^n + 1)^2/32.
G.f.: x*(1 -15*x +27*x^2)/((1-x)*(1-3*x)*(1-9*x)*(1-27*x)).
E.g.f.: (1/32)*(- exp(x) - exp(3*x) + exp(9*x) + exp(27*x)). (End)
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MATHEMATICA
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Table[(9^n-1)*(3^n+1)/32, {n, 0, 30}]
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PROG
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(Magma) [(9^n-1)*(3^n+1)/32: n in [0..40]]; // G. C. Greubel, May 22 2023
(SageMath) [(9^n-1)*(3^n+1)/32 for n in range(41)] # G. C. Greubel, May 22 2023
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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