This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A174425 #23 May 21 2025 06:09:31
%S A174425 23,450,6580,86590,1073071,12803271,148755315,1694786187,19020186047,
%T A174425 210925125565,2316483913054,25237165712764,273094922940644,
%U A174425 2938181887791268,31454145461543161,335264720452385137,3559879862893130917,37671125212625723995,397434517963203503069
%N A174425 Total number of divisors of all n-digit numbers.
%C A174425 Partial sums are A095256.
%H A174425 Andrew Howroyd, <a href="/A174425/b174425.txt">Table of n, a(n) for n = 1..36</a>
%F A174425 From _Andrew Howroyd_, Jan 13 2020: (Start)
%F A174425 a(n) = A006218(10^n-1) - A006218(10^(n-1)-1).
%F A174425 a(n) = A057494(n) - A057494(n-1) - 2*n - 1. (End)
%e A174425 For n = 1; a(1) = 23 because tau (r) of 1-digit numbers r = 1 to 9: {1, 2, 2, 3, 2, 4, 2, 4, 3}. Sum is 23.
%o A174425 (PARI) \\ too slow for n > 20; here b(n) is A006218(n).
%o A174425 b(n)={sum(k=1, sqrtint(n), n\k)*2 - sqrtint(n)^2}
%o A174425 a(n)={b(10^n-1)-b(10^(n-1)-1)} \\ _Andrew Howroyd_, Jan 13 2020
%Y A174425 Cf. A000005, A006218, A057494, A095256.
%K A174425 nonn,base
%O A174425 1,1
%A A174425 _Jaroslav Krizek_, Nov 28 2010
%E A174425 Terms a(11) and beyond from _Andrew Howroyd_, Jan 13 2020