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#26 by Peter Luschny at Wed Oct 18 02:13:54 EDT 2023
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#25 by Michel Marcus at Wed Oct 18 01:30:35 EDT 2023
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#24 by G. C. Greubel at Wed Oct 18 01:27:35 EDT 2023
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#23 by G. C. Greubel at Wed Oct 18 01:27:15 EDT 2023
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| PROG
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(Magma)
A108639:= func< n | (&+[DivisorSigma(j, n-j): j in [0..n-1]]) >;
[A108639(n): n in [1..30]]; // G. C. Greubel, Oct 18 2023
(SageMath)
def A108639(n): return sum(sigma(n-j, j) for j in range(n))
[A108639(n) for n in range(1, 31)] # G. C. Greubel, Oct 18 2023
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| CROSSREFS
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Cf. A109974, A245466 (with k instead of n-k).
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| STATUS
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approved
editing
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#22 by N. J. A. Sloane at Mon Sep 24 16:53:14 EDT 2018
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| EXTENSIONS
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Edited by N. J. A. Sloane at the suggestion of _Andrew S. Plewe_, Jun 08 2007
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Discussion
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| Mon Sep 24
| 16:53
| OEIS Server: https://oeis.org/edit/global/2767
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#21 by Michel Marcus at Tue Dec 26 01:29:34 EST 2017
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#20 by Joerg Arndt at Sun Dec 24 09:22:49 EST 2017
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#19 by Jon E. Schoenfield at Sun Dec 24 01:31:56 EST 2017
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#18 by Jon E. Schoenfield at Sun Dec 24 01:31:53 EST 2017
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| NAME
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a(n) = Sum_{k=1..n} sigma_{n-k}(k), where sigma_m(k) = sum{Sum_{j|k} j^m.
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| EXAMPLE
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a(5) = 1^4 + (1^3 + + 2^3) + (1^2 + + 3^2) + (1^1 + + 2^1 + + 4^1) + (1^0 + + 5^0) = 1 + + 1 + + 8 + + 1 + + 9 + + 1 + + 2 + + 4 + + 1 + + 1 = 29.
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| STATUS
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proposed
editing
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#17 by Michel Marcus at Sun Dec 24 00:51:38 EST 2017
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