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A100176
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Structured octagonal prism numbers.
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3
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1, 16, 63, 160, 325, 576, 931, 1408, 2025, 2800, 3751, 4896, 6253, 7840, 9675, 11776, 14161, 16848, 19855, 23200, 26901, 30976, 35443, 40320, 45625, 51376, 57591, 64288, 71485, 79200, 87451, 96256, 105633, 115600, 126175, 137376, 149221
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history;
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internal format)
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OFFSET
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1,2
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COMMENTS
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Number of divisors of 120^(n-1). - J. Lowell, Aug 30 2008
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LINKS
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FORMULA
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a(n) = 3*n^3 - 2*n^2.
Sum_{n>=1} 1/a(n) = sqrt(3)*Pi/8 - Pi^2/12 + 9*log(3)/8 = 1.0936465529153418... . - Vaclav Kotesovec, Oct 04 2016
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MAPLE
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MATHEMATICA
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PROG
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CROSSREFS
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Cf. A100177 - structured prisms; A100145 for more on structured numbers.
Cf. similar sequences, with the formula (k*n-k+2)*n^2/2, listed in A262000.
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KEYWORD
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nonn,easy
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AUTHOR
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James A. Record (james.record(AT)gmail.com), Nov 07 2004
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EXTENSIONS
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STATUS
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approved
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