|
| |
|
|
A348397
|
|
a(n) = Sum_{d|n} sigma_[n-d](d), where sigma_[k](n) is the sum of the k-th powers of the divisors of n.
|
|
1
|
|
|
|
1, 3, 3, 9, 3, 50, 3, 343, 734, 3388, 3, 133959, 3, 827646, 10297073, 33640713, 3, 2579172499, 3, 44822639761, 678610493345, 285312719194, 3, 393067887861756, 95367431640630, 302875123369476, 150094918113956098, 569940024192528003, 3, 105474401758856279784, 3
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,2
|
|
|
LINKS
|
Michel Marcus, Table of n, a(n) for n = 1..500
|
|
|
FORMULA
|
a(n) = 3 iff n is prime. - Bernard Schott, Oct 17 2021
|
|
|
EXAMPLE
|
a(6) = 50; a(6) = sigma_[6-1](1) + sigma_[6-2](2) + sigma_[6-3](3) + sigma_[6-6](6) = (1^5) + (1^4 + 2^4) + (1^3 + 3^3) + (6^0 + 6^0 + 6^0 + 6^0) = 50.
|
|
|
MATHEMATICA
|
a[n_] := DivisorSum[n, DivisorSigma[n - #, #] &]; Array[a, 30] (* Amiram Eldar, Oct 17 2021 *)
|
|
|
PROG
|
(PARI) a(n) = sumdiv(n, d, sigma(d, n-d)); \\ Michel Marcus, Oct 18 2021
|
|
|
CROSSREFS
|
Cf. A321141.
Sequence in context: A157031 A113213 A088032 * A066572 A307379 A276147
Adjacent sequences: A348394 A348395 A348396 * A348398 A348399 A348400
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Wesley Ivan Hurt, Oct 16 2021
|
|
|
STATUS
|
approved
|
| |
|
|
