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 A239899 #23 Sep 08 2022 08:46:07 %S A239899 2,5,9,89,8009,64152089,4115490587216009, %T A239899 16937262773463574696951813104089 %N A239899 a(0)=2, a(1)=5; thereafter a(n) = product of all preceding terms, minus 1. %H A239899 Robert Munafo, <a href="http://mrob.com/pub/math/nu-sequences.html#table">Some integer sequences</a> %H A239899 Robert Munafo, <a href="http://mrob.com/pub/seq/coprime.html">Mutually coprime sequences</a> %F A239899 a(n) == 8 mod 9, for n > 2. - _Ivan N. Ianakiev_, Apr 06 2014 %F A239899 a(n) = (a(n-1)+1)*a(n-1)-1, for n > 2. - _Zak Seidov_, Apr 06 2014 %e A239899 (9 + 1)*9 - 1 = 89, (89 + 1)*89 - 1 = 8009, (8009 + 1)*8009 - 1 = 64152089. - _Zak Seidov_, Apr 06 2014 %o A239899 (Magma) I:=[2, 5, 9]; [n le 3 select I[n] else Self(n-1)*(Self(n-1)+1)-1: n in [1..10]]; // _Vincenzo Librandi_, May 22 2014 %Y A239899 Cf. A144779-A144784, A239900. %K A239899 nonn %O A239899 0,1 %A A239899 _N. J. A. Sloane_, Apr 05 2014