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Search: id:A152988
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| A152988 |
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Sum of proper divisors minus the number of proper divisors of Catalan number A000108(n). |
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+0
4
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| 0, 0, 0, 0, 7, 47, 193, 236, 1579, 4195, 18461, 62143, 275781, 1131909, 7434169, 10522660, 72469339, 268486155, 1442237845, 4284330539, 18146555293, 62021099893, 248289236937, 798007352239, 2832660377605, 11922780595861
(list; graph; listen)
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OFFSET
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0,5
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FORMULA
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a(n) = A001065(A000108(n))-A032741(A000108(n)) = A152770(A000108(n)).
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EXAMPLE
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a(5)=47 because A000108(5)=42 has 7 proper divisors: 1,2,3,6,7,14,21 and 1+2+3+6+7+14+21-7=47. [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 31 2008]
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MAPLE
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with(numtheory): seq(sigma(binomial(2*n, n)/(n+1))-binomial(2*n, n)/(n+1)-tau(binomial(2*n, n)/(n+1))+1, n = 1 .. 27); [From Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 31 2008]
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CROSSREFS
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Cf. A000005, A000108, A000203, A001065, A032741, A152770.
Sequence in context: A142185 A158914 A046872 this_sequence A009202 A093112 A091516
Adjacent sequences: A152985 A152986 A152987 this_sequence A152989 A152990 A152991
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KEYWORD
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nonn
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AUTHOR
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Omar E. Pol (info(AT)polprimos.com), Dec 20 2008, Jan 07 2009
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EXTENSIONS
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Extended by Emeric Deutsch (deutsch(AT)duke.poly.edu), Dec 31 2008
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