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A366954
The sum of the divisors of the concatenation of 1,2,3,...,n.
0
1, 28, 168, 1854, 19776, 327152, 1244416, 27319968, 178422816, 22222222056, 2075415810048, 308768621226000, 12455031810211128, 2469135782022242640, 197530862561779410288, 21604938101329359719880, 1821571286217135606177024, 270250398197557076360997936
OFFSET
1,2
FORMULA
a(n) = sigma(A007908(n)) = A000203(A007908(n)).
EXAMPLE
a(3)=168 because the divisors of 123 are {1, 3, 41, 123}.
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Sean A. Irvine, Oct 29 2023
STATUS
approved