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Search: id:A153816
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| A153816 |
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a(n)= sum_{i=1...(10^n-1)/9} floor (((10^n-1)/9)/i) |
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+0
3
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| 1, 29, 542, 7967, 105225, 1308095, 15639310, 181976675
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n)=A006218(A002275(n)). Generalized subsequences of A006218(n) are a(n)=A006218(T*A002275(n)), where T>=1, a(n)= sum_{i=1...n} floor (T*(10^n -1)/9*i). For T=9 we have A095256, for T=1 this sequence. The motivation for such sequences is to count the number of elements of length n in a multiplication matrix m*m in base (T+1). In base 10 this gives T=9 and the number of elements of the multiplication matrix m*m of the length n=1,2,3,... digits is given by the sequence b(n)= a(n)- a(n-1), n>=2, a(1)=23.
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CROSSREFS
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Cf. A000005, A095256, A006218, A002275
Sequence in context: A028139 A028137 A028093 this_sequence A028091 A028125 A028134
Adjacent sequences: A153813 A153814 A153815 this_sequence A153817 A153818 A153819
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KEYWORD
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nice,nonn
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AUTHOR
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Ctibor O. Zizka (c.zizka(AT)email.cz), Jan 02 2009
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EXTENSIONS
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Formula corrected by Giovanni Resta (g.resta(AT)iit.cnr.it), Feb 05 2009
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