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 A225105 #7 Apr 30 2013 12:13:09
%S A225105 3,5,7,9,11,13,15,17,19,23,25,29,35,37,39,53,59,61,67,75,79,87,89,99,
%T A225105 101,105,113,115,119,131,149,153,157,173,179,181,187,197,211,219,229,
%U A225105 241,247,249,255,267,269,277,281,307,317,329,349,371,373,383,397
%N A225105 Odd numbers n such that the largest odd term in Collatz(3x+1) trajectory of n is prime.
%H A225105 Reinhard Zumkeller, <a href="/A225105/b225105.txt">Table of n, a(n) for n = 1..10000</a>
%e A225105 15 is in the list since highest odd number in Collatz trajectory of 15 is 53, a prime.
%t A225105 Coll[n_]:=NestWhileList[If[EvenQ[#],#/2,3*# + 1] &,n, #>1&];t={};Do[If[PrimeQ[Max[Select[Coll[n],OddQ]]],AppendTo[t,n]],{n,1,300,2}];t
%o A225105 (Haskell)
%o A225105 a225105 n = a225105_list !! (n-1)
%o A225105 a225105_list = filter
%o A225105 ((== 1) . a010051' . maximum . filter odd . a070165_row) a005408_list
%o A225105 -- _Reinhard Zumkeller_, Apr 30 2013
%Y A225105 Cf. A087232.
%Y A225105 Cf. A010051, A070165, A005408, A220237, A025586.
%K A225105 nonn
%O A225105 1,1
%A A225105 _Jayanta Basu_, Apr 28 2013