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A116913
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Inverse Moebius transform of pentagonal numbers.
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3
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1, 6, 13, 28, 36, 69, 71, 120, 130, 186, 177, 301, 248, 363, 378, 496, 426, 663, 533, 798, 734, 897, 783, 1245, 961, 1254, 1210, 1547, 1248, 1914, 1427, 2016, 1806, 2148, 1926, 2821, 2036, 2685, 2522, 3270, 2502, 3702, 2753, 3801, 3510, 3939, 3291, 5053, 3648
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OFFSET
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1,2
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LINKS
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FORMULA
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a(n) = Sum_{d|n} d*(3*d-1)/2.
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MATHEMATICA
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Table[Sum[d*(3d - 1)/2, {d, Divisors[n]}], {n, 101}] (* Indranil Ghosh, May 23 2017 *)
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PROG
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(PARI) a(n) = sumdiv(n, d, d*(3*d-1)/2); \\ Michel Marcus, Mar 25 2015
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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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EXTENSIONS
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STATUS
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approved
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