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 A055435 #9 Dec 07 2019 08:18:28
%S A055435 0,-1,-3,14,15,15,14,12,9,5,-55,-126,-208,-301,-405,-520,-646,-783,
%T A055435 -931,-1090,-1260,-1441,-1633,-1836,-2050,-2275,-2511,-2758,-3016,
%U A055435 -3285,-3565,12144,12342,12529,12705,12870,13024,13167,13299,13420
%N A055435 (1/18)*Difference between concatenation of n and n^2 and concatenation of n^2 and n.
%F A055435 a(n) = (A053061(n) - A055436(n))/18 = n*(10^floor(2*log_10(W2)+1) - 1 - n*(10^floor(log_10(W2)+1)-1))/18.
%t A055435 Table[((n*10^IntegerLength[x = n^2] + x) - (n^2*10^IntegerLength[n] + n))/18, {n, 40}] (* _Jayanta Basu_, Jul 12 2013 *)
%K A055435 base,easy,sign
%O A055435 1,3
%A A055435 _Henry Bottomley_, May 18 2000