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 A307807 #7 Apr 29 2019 20:36:14
%S A307807 3,0,3,1,2,0,2,2,5,2,1,2,0,0,0,0,1,2,3,0,1,1
%N A307807 Number of palindromic nonagonal numbers with exactly n digits.
%C A307807 Number of terms in A082723 with exactly n digits.
%H A307807 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 A307807 There are only three 3 digit nonagonal numbers that are palindromic, 111, 474 and 969. Thus, a(3)=3.
%t A307807 A082723 = {0, 1, 9, 111, 474, 969, 6666, 18981, 67276, 4411144, 6964696, 15444451, 57966975, 448707844, 460595064, 579696975, 931929139, 994040499, 1227667221, 9698998969, 61556965516, 664248842466, 699030030996, 99451743334715499, 428987160061789824, 950178723327871059, 1757445628265447571, 4404972454542794044, 9433971680861793349, 499583536595635385994, 1637992008558002997361, 19874891310701319847891}; Table[Length[Select[A082723, IntegerLength[#] == n || (n == 1 && # == 0) &]], {n, 22}]
%Y A307807 Cf. A001106, A055560, A082722, A082733, A307801, A307802.
%K A307807 nonn,base,more
%O A307807 1,1
%A A307807 _Robert Price_, Apr 29 2019