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A319194 a(n) = Sum_{k=1..n} sigma(n,k). 5
1, 6, 38, 373, 4461, 68033, 1202753, 24757484, 574608039, 14925278329, 427729375161, 13424413453317, 457608305315211, 16841852554413561, 665483754539870667, 28101844918556128030, 1262901795439193700478, 60182608193322255156347, 3031285556584399354961535 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 1..380

FORMULA

a(n) ~ n^n / (1 - exp(-1)).

a(n) = Sum_{k=1..n} k^n * floor(n/k). - Daniel Suteu, Nov 10 2018

MATHEMATICA

Table[Sum[DivisorSigma[n, k], {k, 1, n}], {n, 1, 20}]

PROG

(PARI) a(n) = sum(k=1, n, sigma(k, n)); \\ Michel Marcus, Sep 13 2018

(PARI) a(n) = sum(k=1, n, k^n * (n\k)); \\ Daniel Suteu, Nov 10 2018

CROSSREFS

Cf. A065805.

Sequence in context: A075197 A276473 A062814 * A303865 A319647 A239983

Adjacent sequences:  A319191 A319192 A319193 * A319195 A319196 A319197

KEYWORD

nonn

AUTHOR

Vaclav Kotesovec, Sep 13 2018

STATUS

approved

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Last modified August 18 08:57 EDT 2019. Contains 326077 sequences. (Running on oeis4.)