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A188138
Sum of sigma_2(k) for 1 <= k <= 10^n, where sigma_2(k) is the sum of the divisors of k squared.
2
1, 469, 407819, 401382971, 400757638164, 400692683389101, 400686363385965077, 400685705322499946270, 400685641565621401132515, 400685635084923815073475174, 400685634458741808360827818508, 400685634393583522561137962683069
OFFSET
0,2
COMMENTS
a(n) ~ 10^(3n)*zeta(3)/3.
LINKS
Hiroaki Yamanouchi, Table of n, a(n) for n = 0..18
MATHEMATICA
k = 1; lst = {}; s = 0; Do[ While[k < 10^n + 1, s = s + DivisorSigma[2, k]; k++]; AppendTo[lst, s], {n, 0, 9}]; lst
a[n_] := With[{nn=10^n}, Sum[Floor[nn/k]*k^2, {k, nn}]]; Array[a, 9, 0] (* T. D. Noe, Apr 25 2011 *)
CROSSREFS
Cf. A072692.
Sequence in context: A250238 A234125 A259423 * A112297 A345522 A345776
KEYWORD
nonn
AUTHOR
Robert G. Wilson v, Apr 25 2011
EXTENSIONS
a(10)-a(11) from Hiroaki Yamanouchi, Jul 06 2014
STATUS
approved