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 A086125 #13 May 31 2025 20:14:23
%S A086125 2,4,8,15,31,128,163,12284
%N A086125 Values of k such that f(k) is a prime, where f(1) = 1, f(i) = prime(i)*f(i-1) + 2.
%C A086125 No additional terms up to k = 1000. - _Harvey P. Dale_, Feb 02 2019
%C A086125 No additional terms up to k = 20000. - _Michael S. Branicky_, May 31 2025
%t A086125 f[1]=1; f[x_] := f[x] = Prime[x]*f[x - 1] + 2; Do[ If[ PrimeQ[ f[n]], Print[n]], {n, 1, 1900}]
%t A086125 nxt[{n_,a_}]:={n+1,a*Prime[n+1]+2}; Select[NestList[nxt,{1,1},200], PrimeQ[ #[[2]]]&][[All,1]] (* _Harvey P. Dale_, Feb 02 2019 *)
%Y A086125 The primes are in A086124.
%Y A086125 Cf. A000668, A076481, A086122, A086123.
%K A086125 more,nonn
%O A086125 1,1
%A A086125 _Labos Elemer_, Jul 23 2003
%E A086125 Edited by _Robert G. Wilson v_, Jul 25 2003
%E A086125 a(8) from _Michael S. Branicky_, May 29 2025