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Search: id:A165929
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| A165929 |
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a(1) = 1, for n > 1: a(n) = sigma(sum of the previous terms) where sigma(k) = sum of the divisors of k. |
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+0
2
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| 1, 1, 3, 6, 12, 24, 48, 120, 264, 480, 1104, 2064, 4128, 10752, 19320, 38328, 91992, 170016, 369600, 745560, 1854720, 3845760, 7765296, 14990520, 29910120, 59856720, 119710416, 298755600, 667297320, 1446528360, 4011171840
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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a(1) = 1, for n > 1: a(n) = sigma(sum_(i=1...n-1) a(i)) = A000203(sum_(i=1...n-1) a(i)). a(n) = inverse of partial sums of A081973(n), i.e. a(1) = A081973(1), for n > 1: a(n) = A081973(n) - A081973(n-1), i.e. first diferences of sequence A081973.
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EXAMPLE
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For n=4 the a(4) = sigma(a(1)+a(2)+a(3)) = sigma(1+1+3) = sigma(5) = 6.
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PROGRAM
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(PARI) print1(1); s=1; for(i=1, 100, k=sigma(s); print1(", "k); s+=k)
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CROSSREFS
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Sequence in context: A007283 A049942 A099844 this_sequence A084717 A102254 A007239
Adjacent sequences: A165926 A165927 A165928 this_sequence A165930 A165931 A165932
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KEYWORD
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nonn
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AUTHOR
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Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), Sep 30 2009
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EXTENSIONS
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Extension and program by Charles R Greathouse IV (charles.greathouse(AT)case.edu), Oct 12 2009
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