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 A173906 #22 Feb 08 2025 10:30:35
%S A173906 16,338,5183,69837,878377,10583772,123837722,1418377223,15983772233,
%T A173906 177837722339,1958377223398,21383772233983,231837722339831,
%U A173906 2498377223398316,26783772233983162,285837722339831620,3038377223398316206,32183772233983162066,339837722339831620668,3578377223398316206680
%N A173906 Total number of digits of the squares of all n-digit numbers.
%C A173906 Sequence inspired by Claudio Meller's email to [seqfan] 07:01 a.m., Nov 26 2010, subject: About a problem of Bernardo Recamán Santos found in http://www.mathpuzzle.com/
%F A173906 Limit_{n->oo} a(n)/(n*10^n) = 9/5. [corrected by _Jason Yuen_, Feb 07 2025]
%F A173906 From _Jason Yuen_, Feb 07 2025: (Start)
%F A173906 a(n) = (2*n-1)*A062940(2*n-1) + (2*n)*A062940(2*n).
%F A173906 a(n) = (9/5)*n*10^n - ceiling((sqrt(10)-1)*10^(n-1)) for n > 1. (End)
%t A173906 f[n_] := Block[{br = 1+ Floor[10^(n-1)*Sqrt@10]},(2n-1)(br-10^(n-1)) + 2n(10^n-br)]; Array[f, 20]
%Y A173906 Cf. A000290, A062940, A113119.
%K A173906 nonn,base
%O A173906 1,1
%A A173906 _Robert G. Wilson v_, Nov 26 2010