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A283078
a(n) = sigma(7*n).
15
8, 24, 32, 56, 48, 96, 57, 120, 104, 144, 96, 224, 112, 171, 192, 248, 144, 312, 160, 336, 228, 288, 192, 480, 248, 336, 320, 399, 240, 576, 256, 504, 384, 432, 342, 728, 304, 480, 448, 720, 336, 684, 352, 672, 624, 576, 384, 992, 400, 744, 576, 784, 432, 960
OFFSET
1,1
LINKS
FORMULA
From Amiram Eldar, Dec 16 2022: (Start)
a(n) = A000203(7*n) = A000203(A008589(n)).
Sum_{k=1..n} a(k) = (55*Pi^2/84) * n^2 + O(n*log(n)). (End)
EXAMPLE
For n = 3, the divisors of 3*7 are {1, 3, 7, 21}. Now, 1 + 3 + 7 + 21 = 32. So, a(3) = 32. - Indranil Ghosh, Feb 28 2017
MATHEMATICA
Table[DivisorSigma[1, 7n], {n, 1, 54}] (* Indranil Ghosh, Feb 28 2017 *)
PROG
(PARI) a(n) = sigma(7*n) \\ Indranil Ghosh, Feb 28 2017
CROSSREFS
Sigma(k*n): A000203 (k=1), A062731 (k=2), A144613 (k=3), A193553 (k=4), A283118 (k=5), A224613 (k=6), this sequence (k=7), A283122 (k=8), A283123 (k=9).
Cf. A008589.
Sequence in context: A028628 A333427 A128690 * A319528 A140403 A108578
KEYWORD
nonn
AUTHOR
Seiichi Manyama, Feb 28 2017
STATUS
approved