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Search: id:A086665
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| 1, 1, 1, 3, 1, 7, 1, 9, 7, 11, 1, 21, 1, 15, 16, 23, 1, 31, 1, 33, 22, 23, 1, 51, 21, 27, 31, 45, 1, 62, 1, 53, 34, 35, 36, 81, 1, 39, 40, 79, 1, 84, 1, 69, 67, 47, 1, 113, 43, 81, 52, 81, 1, 109, 56, 107, 58, 59, 1, 156
(list; graph; listen)
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OFFSET
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1,4
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EXAMPLE
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a(10)=sigma(10)-(2+5)=1+2+5+10-7=11
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MATHEMATICA
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sigma1 = Table[Plus @@ Divisors[n], {n, 100}]; sopfr = Prepend[ Array[ Plus @@ Map[ Times @@ #1 &, FactorInteger[ # ] ] &, 100, 2 ], 0 ]; Table[sigma1[[n]] - sopfr[[n]], {n, 100}] - Alonso Delarte (alonso.delarte(AT)gmail.com), Dec 01 2004
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PROGRAM
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(PARI) sodf(n)=local(x); x=factor(n); sum(i=1, length(x[, 1]), sum(j=1, x[i, 2], x[i, 1])); for(i=1, 60, print1(sigma(i)-sodf(i)", "))
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CROSSREFS
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Cf. A001414, A000203.
Sequence in context: A163117 A099749 A077202 this_sequence A050521 A098093 A114712
Adjacent sequences: A086662 A086663 A086664 this_sequence A086666 A086667 A086668
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KEYWORD
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nonn
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AUTHOR
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Jon Perry (perry(AT)globalnet.co.uk), Jul 27 2003
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