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 A091628 #24 Sep 08 2022 08:45:13 %S A091628 23,223,2223,22223,222223,2222223,22222223,222222223,2222222223, %T A091628 22222222223,222222222223,2222222222223,22222222222223, %U A091628 222222222222223,2222222222222223,22222222222222223,222222222222222223 %N A091628 Concatenation of n 2's followed by 3. %C A091628 Sequence arising in _Farideh Firoozbakht_'s solution to Prime Puzzle 251; 23 is the only pointer prime (A089823) not containing the digit "1". %H A091628 Tanya Khovanova, <a href="http://www.tanyakhovanova.com/RecursiveSequences/RecursiveSequences.html">Recursive Sequences</a> %H A091628 Carlos Rivera's Prime Puzzles and Problems Connection, <a href="http://www.primepuzzles.net/puzzles/puzz_251.htm">Puzzle 251, Pointer primes</a> %H A091628 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (11,-10). %F A091628 a(n) = (10^(n+1) - 1)/9*2 + 1. %F A091628 a(n) = 10*a(n-1) - 7, with a(1)=23. - _Vincenzo Librandi_, Nov 16 2010 %F A091628 From _Colin Barker_, May 06 2012: (Start) %F A091628 a(n) = 11*a(n-1) - 10*a(n-2). %F A091628 G.f.: x*(23-30*x)/((1-x)*(1-10*x)). (End) %o A091628 (Magma) [ n eq 1 select 23 else 10*Self(n-1)-7: n in [1..17] ]; %Y A091628 Cf. A089823, A091629, A091630, A091631, A091632. %K A091628 base,easy,nonn %O A091628 1,1 %A A091628 _Enoch Haga_, Jan 24 2004 %E A091628 Edited and extended by _Ray Chandler_, Feb 07 2004