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A287926
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Sum of the divisors of n that are not divisible by 49.
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3
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1, 3, 4, 7, 6, 12, 8, 15, 13, 18, 12, 28, 14, 24, 24, 31, 18, 39, 20, 42, 32, 36, 24, 60, 31, 42, 40, 56, 30, 72, 32, 63, 48, 54, 48, 91, 38, 60, 56, 90, 42, 96, 44, 84, 78, 72, 48, 124, 8, 93, 72, 98, 54, 120, 72, 120, 80, 90, 60, 168, 62, 96, 104, 127, 84, 144
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OFFSET
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1,2
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LINKS
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Seiichi Manyama, Table of n, a(n) for n = 1..10000
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FORMULA
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Multiplicative with a(7^e) = 8 and a(p^e) = (p^(e+1)-1)/(p-1) otherwise. - Amiram Eldar, Sep 17 2020
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MATHEMATICA
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f[p_, e_] := If[p == 7, 8, (p^(e+1)-1)/(p-1)]; a[1] = 1; a[n_] := Times @@ f @@@ FactorInteger[n]; Array[a, 100] (* Amiram Eldar, Sep 17 2020 *)
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PROG
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(PARI) a(n)=sumdiv(n, d, ((d%49)>0)*d); \\ Andrew Howroyd, Jul 20 2018
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CROSSREFS
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Cf. A000203, A213598.
Sum of the divisors of n that are not divisible by k: A046913 (k=3), A046897 (k=4), A116073 (k=5), A284326 (k=6), A113957 (k=7), A284341 (k=8), A116607 (k=9), A284344 (k=10), A227131 (k=25), this sequence (k=49).
Sequence in context: A325316 A227131 A097863 * A097012 A143348 A000203
Adjacent sequences: A287923 A287924 A287925 * A287927 A287928 A287929
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KEYWORD
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nonn,mult
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AUTHOR
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Seiichi Manyama, Jun 15 2017
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EXTENSIONS
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Keyword:mult added by Andrew Howroyd, Jul 20 2018
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STATUS
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approved
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