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 A090368 #29 Nov 15 2022 02:37:17
%S A090368 1,3,5,7,3,11,13,3,17,19,3,23,5,3,29,31,3,5,37,3,41,43,3,47,7,3,53,5,
%T A090368 3,59,61,3,5,67,3,71,73,3,7,79,3,83,5,3,89,7,3,5,97,3,101,103,3,107,
%U A090368 109,3,113,5,3,7,11,3,5,127,3,131,7,3,137,139,3,11,5,3,149,151,3,5,157,3,7
%N A090368 a(1) = 1; for n > 1, smallest divisor > 1 of 2n-1.
%C A090368 For n > 1, a(n) is an odd prime. - _Chai Wah Wu_, Nov 14 2022
%H A090368 Remi Eismann, <a href="/A090368/b090368.txt">Table of n, a(n) for n = 1..10000</a>
%t A090368 Join[{1},Divisors[#][[2]]&/@Range[3,161,2]] (* _Harvey P. Dale_, Oct 09 2011 *)
%t A090368 a[n_] := FactorInteger[2*n-1][[1,1]]; Array[a, 80] (* _Amiram Eldar_, Jun 11 2022 *)
%o A090368 (PARI) a(n)=if(n>1, factor(2*n-1)[1,1], 1) \\ _Charles R Greathouse IV_, Nov 09 2016
%o A090368 (Python)
%o A090368 from sympy import primefactors
%o A090368 def A090368(n): return min(primefactors((n<<1)-1), default=1) # _Chai Wah Wu_, Nov 14 2022
%Y A090368 Bisection of A020639.
%Y A090368 Cf. A100773.
%K A090368 nonn
%O A090368 1,2
%A A090368 _Lekraj Beedassy_, Nov 27 2003
%E A090368 More terms from _Ray Chandler_, Dec 02 2003
%E A090368 Definition corrected by _Rémi Eismann_, May 08 2007