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%I #5 Oct 29 2023 23:04:32
%S 1,28,168,1854,19776,327152,1244416,27319968,178422816,22222222056,
%T 2075415810048,308768621226000,12455031810211128,2469135782022242640,
%U 197530862561779410288,21604938101329359719880,1821571286217135606177024,270250398197557076360997936
%N The sum of the divisors of the concatenation of 1,2,3,...,n.
%F a(n) = sigma(A007908(n)) = A000203(A007908(n)).
%e a(3)=168 because the divisors of 123 are {1, 3, 41, 123}.
%Y Cf. A007908, A000203, A110756, A075019, A075022.
%K nonn,base
%O 1,2
%A _Sean A. Irvine_, Oct 29 2023