A136363 a(n) = Sum_{ composite k, 1 <= k <= 10^n} (Sum of divisors d of k with 1 < d < k).
23, 3150, 321582, 32241015, 3224590836, 322466618438, 32246696794797, 3224670272194238, 322467032612360629, 32246703337400266401, 3224670334173560419030, 322467033423857340138979, 32246703342405509396897775, 3224670334241078180927002518, 322467033424112509326065894640
Offset: 1
Keywords
Examples
a(1) = 23 because the divisors through 10^1 are as follows: 4 (2); 6 (2,3); 8 (2,4); 9 (3); 10 (2,5). The sum is 2 + 2 + 3 + 2 + 4 + 3 + 2 + 5 = 23.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..36 (calculated using the b-file at A072692)
Formula
a(n) = A072692(n) - 10^n*(10^n+3)/2 + 1. - Max Alekseyev, May 10 2009
a(n) ~ (Pi^2/12 - 1/2) * 10^(2*n). - Amiram Eldar, Aug 05 2024
Extensions
Edited by N. J. A. Sloane, Jan 12 2008
Extended by Max Alekseyev, May 10 2009
a(13)-a(15) from Amiram Eldar, Aug 05 2024