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 A020337 #20 Apr 06 2021 04:55:18 %S A020337 10,20,30,40,50,60,70,80,738,820,902,984,1066,1148,1230,1312,1394, %T A020337 1476,1558,1640,1722,1804,1886,1968,2050,2132,2214,2296,2378,2460, %U A020337 2542,2624,2706,2788,2870,2952,3034,3116,3198,3280,3362,3444,3526,3608,3690,3772 %N A020337 Numbers whose base-9 representation is the juxtaposition of two identical strings. %H A020337 Amiram Eldar, <a href="/A020337/b020337.txt">Table of n, a(n) for n = 1..10000</a> %F A020337 a(n) = n*9^floor(log_9(n)+1) + n. - _Ilya Gutkovskiy_, Jan 26 2018 %e A020337 902_10 = 1212_9. - _Jon E. Schoenfield_, Feb 12 2021 %t A020337 a[n_] := n + n*9^Floor[Log[9, n] + 1]; Array[a, 50] (* _Amiram Eldar_, Apr 06 2021 *) %Y A020337 Cf. A020330, A020331, A020332, A020333, A020334, A020335, A020336, A020338. %K A020337 nonn,base %O A020337 1,1 %A A020337 _David W. Wilson_, Melia Aldridge (ma38(AT)spruce.evansville.edu)