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 A092696 #12 Aug 11 2024 14:41:34 %S A092696 1212121,12121212121,1212121212121212121212121212121212121212121 %N A092696 Smoothly undulating palindromic primes of the form (12*10^n-21)/99. %C A092696 The De Geest link calls these smoothly undulating palindromic primes. Corresponding n are given in A062209. Equivalently, primes of the form 1212...121: Decimal digits "12" repeated k times with 1 appended (or "21" repeated k times with 1 prefixed). Corresponding k are given in A056803. The next term, a(4), has "12" repeating A056803(4) = 69 times and length A062209(4) = 2*A056803(4) + 1 = 139 decimal digits. %H A092696 P. De Geest, <a href="https://www.worldofnumbers.com/undulat.htm">SUPP Reference Table</a> %H A092696 <a href="/index/Pri#pri_supp">Index entries for sequences related to smoothly undulating palindromic primes</a> %F A092696 a(n) = (4*10^A062209(n)-7)/33. - _M. F. Hasler_, Jul 30 2015 %Y A092696 Cf. A056803 (number of 12's (or 21's)), A062209 (corresponding decimal digit lengths). %Y A092696 Cf. A032758, A033619, A030291, A059168, A242541, A004022. %K A092696 bref,nonn,base %O A092696 1,1 %A A092696 _Rick L. Shepherd_, Mar 04 2004 %E A092696 Edited by _M. F. Hasler_, Jul 30 2015