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 A121390 #4 Apr 08 2020 14:02:47 %S A121390 2,8607769,25823309,222281113118699,5740034091209256896999, %T A121390 1275901167133279185594625154673899999, %U A121390 7323716196358702385046852882006552347670105360888299999999 %N A121390 Sequence generated by the recurrence below begins with exactly seven primes. %C A121390 This sequence has the smallest value of a(1) for a(0) = 2 and this recurrence such that the first seven terms are primes. The first composite term is too large to include. Note also that each a(n) has Fibonacci(n) trailing 9's (see A121389). %F A121390 a(0) = 2; a(1) = 8607769; a(n) = a(n-2)*a(n-1) + a(n-2) + a(n-1). %e A121390 a(2) = 25823309 = 2*8607769 + 2 + 8607769 and is prime. %Y A121390 Cf. A000045, A063896, A121389. %K A121390 nonn %O A121390 0,1 %A A121390 _Rick L. Shepherd_, Jul 26 2006