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A343781 a(n) = Sum_{k=1..floor(n/2)} sigma_k(n-k), where sigma_k(n) is the sum of the k-th powers of the divisors of n. 3
0, 1, 3, 9, 17, 55, 111, 457, 943, 4962, 11148, 69526, 159402, 1161340, 2765874, 22829766, 55192956, 510771772, 1257880780, 12870681814, 32042113008, 359566186586, 904795505226, 11043196798176, 28002785395660, 369463867367567, 943392140873807, 13378621275148931 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,3
LINKS
EXAMPLE
a(5) = 17; a(5) = Sum_{i=1..2} sigma_k(5-k) = sigma_1(4) + sigma_2(3) = (1+2+4) + (1^2+3^2) = 7 + 10 = 17.
MATHEMATICA
Table[Sum[DivisorSigma[i, n - i], {i, Floor[n/2]}], {n, 30}]
PROG
(PARI) a(n) = sum(k=1, n\2, sigma(n-k, k)); \\ Michel Marcus, Apr 29 2021
CROSSREFS
Cf. A245466.
Sequence in context: A173140 A018307 A108050 * A321869 A009211 A105538
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, Apr 29 2021
STATUS
approved

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Last modified March 29 08:13 EDT 2024. Contains 371265 sequences. (Running on oeis4.)