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A082050
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Sum of divisors of n that are not of the form 3k+1.
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1
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0, 2, 3, 2, 5, 11, 0, 10, 12, 7, 11, 23, 0, 16, 23, 10, 17, 38, 0, 27, 24, 13, 23, 55, 5, 28, 39, 16, 29, 61, 0, 42, 47, 19, 40, 86, 0, 40, 42, 35, 41, 88, 0, 57, 77, 25, 47, 103, 0, 57, 71, 28, 53, 119, 16, 80, 60, 31, 59, 153, 0, 64, 96, 42, 70, 121, 0, 87, 95, 56, 71, 190
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| a(A004611(n))=0.
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FORMULA
| G.f.: Sum(x^(2*k)*(2+3*x^k+x^(3*k))/(1-x^(3*k))^2,k=1..infinity). - Vladeta Jovovic (vladeta(AT)eunet.rs), Apr 11 2006
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MATHEMATICA
| sd[n_]:=Total[Select[Divisors[n], !IntegerQ[(#-1)/3]&]]; Array[sd, 80] (* From Harvey P. Dale, May 04 2011 *)
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PROG
| (PARI) for(n=1, 100, print1(sumdiv(n, d, if(d%3!=1, d))", "))
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CROSSREFS
| Cf. A000203, A046913, A078181, A078182, A082051, A027748.
Sequence in context: A050159 A147294 A059098 * A183098 A183101 A162687
Adjacent sequences: A082047 A082048 A082049 * A082051 A082052 A082053
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KEYWORD
| nonn,easy
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AUTHOR
| Ralf Stephan (ralf(AT)ark.in-berlin.de), Apr 02 2003
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