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 A209188 #18 Dec 22 2024 12:17:53
%S A209188 5,11,19,29,41,5,71,89,109,131,5,181,11,239,271,5,11,379,419,461,5,19,
%T A209188 599,11,701,5,811,11,929,991,5,19,29,1259,11,5,1481,1559,11,1721,5,31,
%U A209188 1979,2069,2161,5,2351,31,2549
%N A209188 Smallest prime factor of n^2 + n - 1.
%H A209188 Vincenzo Librandi, <a href="/A209188/b209188.txt">Table of n, a(n) for n = 2..1000</a>
%H A209188 PrimeFan, <a href="http://primefan.tripod.com/EsotericIntegerSequences.html">Listing of Esoteric Integer Sequences</a>
%H A209188 PrimeFan, <a href="/A031214/a031214.pdf">Esoteric Integer Sequences</a> [Cached copy]
%t A209188 SPF[n_] := (FactorInteger[n])[[1]][[1]]; Flatten[Table[SPF[n^2 + (n - 1)], {n, 2, 50}]]
%t A209188 Table[FactorInteger[n^2+n-1][[1,1]],{n,2,50}] (* _Harvey P. Dale_, Aug 20 2014 *)
%o A209188 (Magma) [Min(PrimeFactors(n^2+n-1)):n in[2..70]];// _Vincenzo Librandi_, Sep 18 2016
%o A209188 (PARI) a(n) = vecmin(factor(n^2+n-1)[,1]); \\ _Michel Marcus_, Sep 18 2016
%Y A209188 Cf. A071182.
%K A209188 nonn
%O A209188 2,1
%A A209188 _N. J. A. Sloane_, Mar 05 2012