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Search: id:A049820
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| 0, 0, 1, 1, 3, 2, 5, 4, 6, 6, 9, 6, 11, 10, 11, 11, 15, 12, 17, 14, 17, 18, 21, 16, 22, 22, 23, 22, 27, 22, 29, 26, 29, 30, 31, 27, 35, 34, 35, 32, 39, 34, 41, 38, 39, 42, 45, 38, 46, 44, 47, 46, 51, 46, 51, 48, 53, 54, 57, 48, 59, 58, 57, 57, 61, 58, 65
(list; graph; listen)
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OFFSET
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1,5
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COMMENT
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a(n)=number of positive numbers in n-th row of array T given by A049816.
Also equal to the number of partitions p of n such that max(p)-min(p) = 1. - Giovanni Resta (g.resta(AT)iit.cnr.it), Feb 06 2006. E.g. a(7)=5 because we have [4,3],[3,2,2],[2,2,2,1],[2,2,1,1,1] and [2,1,1,1,1,1]. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 01 2006
a(n) = number of non-divisors of n. [From Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), Nov 14 2009]
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FORMULA
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a(n)=sum(k=1, n, ceil(n/k)-floor(n/k)) - Benoit Cloitre (benoit7848c(AT)orange.fr), May 11 2003
G:=sum(x^(2*k+1)/(1-x^k)/(1-x^(k+1)),k=1..infinity); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Mar 01 2006
a(n) = A006590(n) - A006218(n) = A161886(n) - A000005(n) - A006218(n) + 1 for n >= 1. [From Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), Nov 14 2009]
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MAPLE
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with(numtheory); A049820 := n->n-sigma[0](n);
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PROGRAM
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(PARI) a(n)=n-numdiv(n)
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CROSSREFS
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Cf. A000005, A062249.
Sequence in context: A062327 A075491 A089279 this_sequence A109712 A095049 A118209
Adjacent sequences: A049817 A049818 A049819 this_sequence A049821 A049822 A049823
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KEYWORD
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nonn,easy
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AUTHOR
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Clark Kimberling (ck6(AT)evansville.edu)
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