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 A236369 #11 Nov 04 2017 18:33:27 %S A236369 2,2,10,3430,281192563951390, %T A236369 1766847064778382532572997586311708103976882383055495099549785723721857950 %N A236369 4^n! - 3^n! + 2^n! - 1. %C A236369 The next term has 434 digits. - _Harvey P. Dale_, Nov 04 2017 %F A236369 a(n)=4^n!-3^n!+2^n!-1. %e A236369 For n=2, a(2)=4^2!-3^2!+2^2!-1=16-9+4-1=10. %t A236369 4^#-3^#+2^#-1&/@(Range[0,5]!) (* _Harvey P. Dale_, Nov 04 2017 *) %o A236369 (PARI) a(n)=(k->4^k-3^k+2^k-1)(n!) \\ _Charles R Greathouse IV_, Jan 23 2014 %Y A236369 Cf. A203925, A236368. %K A236369 nonn %O A236369 0,1 %A A236369 _Assoul Abdelkarim_, Jan 23 2014 %E A236369 a(4)-a(5) from _Charles R Greathouse IV_, Jan 23 2014