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 A307801 #5 Apr 29 2019 20:35:58
%S A307801 3,0,0,1,0,0,0,0,4,0,0,2,3,1,0,1,0,0,1,0
%N A307801 Number of palindromic octagonal numbers with exactly n digits.
%C A307801 Number of terms in A057107 with exactly n digits.
%H A307801 G. J. Simmons, <a href="/A002778/a002778_2.pdf">Palindromic powers</a>, J. Rec. Math., 3 (No. 2, 1970), 93-98. [Annotated scanned copy] See page 95.
%e A307801 There is only one 4 digit octagonal number that is palindromic, 8008. Thus, a(4)=1.
%t A307801 A057107 = {0, 1, 8, 8008, 120232021, 124060421, 161656161, 185464581, 544721127445, 616947749616, 3333169613333, 3333802083333, 6506939396056, 12212500521221, 5466543663456645, 3310988011108890133, 520752145595541257025, 336753352502205253357633, 5882480463134313640842885, 102573006711888117600375201, 8025741496504444056941475208, 18651903272292929227230915681, 33582545421505050512454528533}; Table[Length[Select[A054910, IntegerLength[#] == n || (n == 1 && # == 0) &]], {n, 20}] (* _Robert Price_, Apr 29 2019 *)
%Y A307801 Cf. A000567, A057107, A057106, A059870, A307790, A307791.
%K A307801 nonn,base,more
%O A307801 1,1
%A A307801 _Robert Price_, Apr 29 2019