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A358859
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a(n) is the smallest n-gonal number divisible by exactly n n-gonal numbers.
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3
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6, 36, 210, 4560, 6426, 326040, 4232250, 1969110, 296676380, 4798080, 166289760, 73765692000, 712750500, 50561280, 33944067893736, 2139168754800, 4292572951800, 1414764341760, 72461756727360, 180975331456920, 1870768457500800, 5498331930000, 153698278734000
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OFFSET
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3,1
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COMMENTS
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The corresponding indices of n-gonal numbers are 3, 6, 12, 48, 51, 330, 1100, 702, ...
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LINKS
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Table of n, a(n) for n=3..25.
Eric Weisstein's World of Mathematics, Polygonal Number
Index entries for sequences related to divisors of numbers
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EXAMPLE
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a(5) = 210, because 210 is a pentagonal number that has 5 pentagonal divisors {1, 5, 35, 70, 210} and this is the smallest such number.
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PROG
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(PARI) a(n) = if(n<3, return()); for(k=1, oo, my(t=(k*(n*k - n - 2*k + 4))\2); if(sumdiv(t, d, ispolygonal(d, n)) == n, return(t))); \\ Daniel Suteu, Dec 04 2022
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CROSSREFS
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Cf. A005179, A076983, A358539, A358860, A358861.
Sequence in context: A357027 A357093 A357029 * A357091 A268454 A171280
Adjacent sequences: A358856 A358857 A358858 * A358860 A358861 A358862
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KEYWORD
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nonn
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AUTHOR
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Ilya Gutkovskiy, Dec 03 2022
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EXTENSIONS
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a(11)-a(25) from Daniel Suteu, Dec 04 2022
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STATUS
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approved
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