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 A063042 #6 May 27 2013 03:30:48 %S A063042 3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36, %T A063042 18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7, %U A063042 36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9,3,7,36,18,9 %N A063042 Collatz-2 (A063041) trajectory starting at 3. %C A063042 a(0) = a(5) = 3 %F A063042 a(0) = 3 and a(n) = A063041(a(n-1)) for n > 0 %t A063042 NestList[If[PrimeQ[#],#*Prime[PrimePi[#]-1]+1,#/Min@@First/@FactorInteger[#]]&,3,104] (* _Jayanta Basu_, May 27 2013 *) %Y A063042 A063041. %K A063042 nonn,easy %O A063042 0,1 %A A063042 _Reinhard Zumkeller_, Jul 07 2001