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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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2
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1, 29, 542, 7967, 105225, 1308095, 15639310, 181976675, 2075608136, 23314508721, 258729364359, 2843136431305, 30989792180446, 335482200606705, 3610664794156597, 38665075822637767, 412235037037411453
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| 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
| Cf. A000005, A095256, A006218, A002275
Sequence in context: A028139 A028137 A028093 * A028091 A028125 A028134
Adjacent sequences: A153813 A153814 A153815 * A153817 A153818 A153819
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KEYWORD
| nice,nonn
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AUTHOR
| Ctibor O. Zizka (c.zizka(AT)email.cz), Jan 02 2009
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EXTENSIONS
| Formula corrected by Giovanni Resta (g.resta(AT)iit.cnr.it), Feb 05 2009
a(9)-a(17) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Sep 06 2010
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