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 A217590 #34 Aug 05 2018 12:07:39 %S A217590 4,9,25,68,196,581,1731,5180,15534,46579,139713,419116,1257320 %N A217590 Values in A091579 that need to be smoothed in order to produce A091588. %C A217590 a(n) = A091588(n) + 1 for n >= 1. %C A217590 Each term is roughly 3 times the previous term. %H A217590 F. J. van de Bult, D. C. Gijswijt, J. P. Linderman, N. J. A. Sloane and Allan Wilks, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL10/Sloane/sloane55.html">A Slow-Growing Sequence Defined by an Unusual Recurrence</a>, J. Integer Sequences, Vol. 10 (2007), #07.1.2. See Eq. (28). %H A217590 F. J. van de Bult, D. C. Gijswijt, J. P. Linderman, N. J. A. Sloane and Allan Wilks, A Slow-Growing Sequence Defined by an Unusual Recurrence [<a href="http://neilsloane.com/doc/gijs.pdf">pdf</a>, <a href="http://neilsloane.com/doc/gijs.ps">ps</a>]. See Eq. (28). %H A217590 <a href="/index/Ge#Gijswijt">Index entries for sequences related to Gijswijt's sequence</a> %F A217590 I would very much like a formula for this sequence! %Y A217590 Cf. A090822, A091579, A091587, A091588. %K A217590 nonn,more %O A217590 1,1 %A A217590 _N. J. A. Sloane_, Mar 18 2013