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 A131604 #12 Feb 19 2021 05:55:28 %S A131604 2,67,71,151,157,199,257,263,277,281,311,359,373,401,461,467,499,503, %T A131604 521,523,541,563,571,577,613,641,661,673,677,733,739,743,761,809,829, %U A131604 859,863,911,929,941,967,983,991,1019,1031,1051,1063,1093,1103,1123 %N A131604 Primes of the form r(r(r(r(r(r(r(k)+1)+1)+1)+1)+1)+1)+1, where r(k) = A141468(k) = k-th nonprime. %e A131604 At k=3, we have %e A131604 r(r(r(r(r(r(r(3)+1)+1)+1)+1)+1)+1)+1 %e A131604 = r(r(r(r(r(r(4+1)+1)+1)+1)+1)+1)+1 %e A131604 = r(r(r(r(r(r(5)+1)+1)+1)+1)+1)+1 %e A131604 = r(r(r(r(r(8+1)+1)+1)+1)+1)+1 %e A131604 = r(r(r(r(r(9)+1)+1)+1)+1)+1 %e A131604 = r(r(r(r(14+1)+1)+1)+1)+1 %e A131604 = r(r(r(r(15)+1)+1)+1)+1 %e A131604 = r(r(r(22+1)+1)+1)+1 %e A131604 = r(r(r(23)+1)+1)+1 %e A131604 = r(r(33+1)+1)+1 %e A131604 = r(r(34)+1)+1 %e A131604 = r(48+1)+1 %e A131604 = r(49)+1 %e A131604 = 66+1 %e A131604 = 67. %Y A131604 Cf. A000040, A141468. %K A131604 nonn,less %O A131604 1,1 %A A131604 _Juri-Stepan Gerasimov_, Aug 25 2008 %E A131604 211 removed, 355 replaced by 359 and extended by _R. J. Mathar_, Sep 05 2008