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 A138962 #15 May 27 2022 08:11:55
%S A138962 1,3,3,29,3,3,19,3,3,457,3,3,16087,3,3,35963,3,3,167,3,3,7,3,3,13,3,3,
%T A138962 953,3,3,7,3,3,548636579,3,3,19,3,3,71,3,3,13,3,3,89,3,3,114689,3,3,
%U A138962 17,3,3,12037,3,3,7,3,3
%N A138962 a(1) = 1, a(n) = the smallest prime divisor of A138793(n).
%C A138962 a(61) > 10^11. - _Robert Price_, Mar 22 2015
%H A138962 Daniel Suteu, <a href="/A138962/b138962.txt">Table of n, a(n) for n = 1..333</a>
%F A138962 a(n) = A020639(A138793(n)). - _Daniel Suteu_, May 27 2022
%t A138962 b = {}; a = {}; Do[w = RealDigits[n]; w = First[w]; Do[AppendTo[a, w[[k]]], {k, 1, Length[w]}]; p = FromDigits[Reverse[a]]; AppendTo[b, First[First[FactorInteger[p]]]], {n, 1, 31}]; b (* _Artur Jasinski_, Apr 04 2008 *)
%t A138962 lst = {}; Table[First[First[FactorInteger[FromDigits[Reverse[lst = Join[lst,IntegerDigits[n]]]]]]], {n, 1, 60}] (* _Robert Price_, Mar 22 2015 *)
%o A138962 (PARI)
%o A138962 f(n) = my(D = Vec(concat(apply(s->Str(s), [1..n])))); eval(concat(vector(#D, k, D[#D-k+1]))); \\ A138793
%o A138962 a(n) = my(k=f(n)); forprime(p=2, 10^6, if(k%p == 0, return(p))); if(n == 1, 1, vecmin(factor(k)[,1])); \\ _Daniel Suteu_, May 27 2022
%Y A138962 Cf. A020639, A138793, A104759, A000422, A116504, A007908, A116505, A104759, A075019, A075020, A075021, A075022, A138789, A138790, A138960, A138962.
%K A138962 nonn
%O A138962 1,2
%A A138962 _Artur Jasinski_, Apr 04 2008
%E A138962 a(32)-a(60) from _Robert Price_, Mar 22 2015