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 A172156 #16 Sep 08 2022 08:45:50 %S A172156 7,17,37,157,317,1277,2557,20477,655357,5242877,671088637,2684354557, %T A172156 5368709117,343597383677,23058430092136939517,23611832414348226068477, %U A172156 48357032784585166988247037,830767497365572420564879412675215357 %N A172156 Primes in the chain of repeated application of x->2*x+3, starting at x=2. %H A172156 Vincenzo Librandi, <a href="/A172156/b172156.txt">Table of n, a(n) for n = 1..37</a> %t A172156 Rest[Select[NestList[2#+3&,2,500],PrimeQ]] (* _Harvey P. Dale_, Nov 17 2012 *) %o A172156 (Magma) x:=2; a:=[n eq 1 select 2*x+3 else 2*Self(n-1)+3: n in [1..120]]; [a[i]: i in [1..#a] | IsPrime(a[i])]; // _Bruno Berselli_, May 14 2013 %Y A172156 Cf. A154117. [_Klaus Brockhaus_, Feb 28 2010] %K A172156 nonn %O A172156 1,1 %A A172156 _Vincenzo Librandi_, Jan 27 2010