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 A020335 #20 Apr 06 2021 10:00:58 %S A020335 8,16,24,32,40,48,350,400,450,500,550,600,650,700,750,800,850,900,950, %T A020335 1000,1050,1100,1150,1200,1250,1300,1350,1400,1450,1500,1550,1600, %U A020335 1650,1700,1750,1800,1850,1900,1950,2000,2050,2100,2150,2200,2250,2300,2350 %N A020335 Numbers whose base-7 representation is the juxtaposition of two identical strings. %H A020335 Amiram Eldar, <a href="/A020335/b020335.txt">Table of n, a(n) for n = 1..10000</a> %F A020335 a(n) = n*7^floor(log_7(n)+1) + n. - _Ilya Gutkovskiy_, Jan 26 2018 %e A020335 450_10 = 1212_7. - _Jon E. Schoenfield_, Feb 12 2021 %t A020335 a[n_] := n + n*7^Floor[Log[7, n] + 1]; Array[a, 50] (* _Amiram Eldar_, Apr 06 2021 *) %Y A020335 Cf. A020330, A020331, A020332, A020333, A020334, A020336, A020337, A020338. %K A020335 nonn,base %O A020335 1,1 %A A020335 _David W. Wilson_, Melia Aldridge (ma38(AT)spruce.evansville.edu)