A366954 The sum of the divisors of the concatenation of 1,2,3,...,n.

1, 28, 168, 1854, 19776, 327152, 1244416, 27319968, 178422816, 22222222056, 2075415810048, 308768621226000, 12455031810211128, 2469135782022242640, 197530862561779410288, 21604938101329359719880, 1821571286217135606177024, 270250398197557076360997936

Offset: 1

Author

Sean A. Irvine, Oct 29 2023

Keywords

• nonn
• base

Examples

			a(3)=168 because the divisors of 123 are {1, 3, 41, 123}.
		

Crossrefs

Cf. A007908, A000203, A110756, A075019, A075022.

Formula

a(n) = sigma(A007908(n)) = A000203(A007908(n)).