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 A038802 #22 Jul 29 2016 00:53:53
%S A038802 1,2,3,1,4,5,1,6,7,1,8,2,1,9,10,1,2,11,1,12,13,1,14,3,1,15,2,1,16,17,
%T A038802 1,2,18,1,19,20,1,3,21,1,22,2,1,23,3,1,2,24,1,25,26,1,27,28,1,29,2,1,
%U A038802 3,4,1,2,30,1,31,3,1,32,33,1,4,2,1,34,35,1,2,36
%N A038802 Factor 2n+1 = (2^m1)*(3^m2)*(5^m3)*...; a(n) = number of initial zero exponents.
%H A038802 T. D. Noe, <a href="/A038802/b038802.txt">Table of n, a(n) for n = 1..1000</a>
%F A038802 a(n) = A049084(A020639(2n+1))-1. - _R. J. Mathar_, Mar 01 2011
%e A038802 9 = (2^0)*(3^2), thus a(4) = 1.
%p A038802 A038802 := proc(n) numtheory[factorset](2*n+1) ; min(%); numtheory[pi](%)-1 ; end proc: # _R. J. Mathar_, Mar 01 2011
%t A038802 Table[f = FactorInteger[2 n + 1]; PrimePi[f[[1, 1]]] - 1, {n, 100}] (* _T. D. Noe_, Apr 23 2013 *)
%o A038802 (PARI) lpf(n)=factor(n)[1,1]
%o A038802 a(n)=primepi(lpf(2*n+1))-1 \\ _Charles R Greathouse IV_, Jul 29 2016
%K A038802 nonn
%O A038802 1,2
%A A038802 _Thomas Kellar_
%E A038802 a(69) corrected by _Rick G. Rosner_, Apr 22 2013