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 A209190 #42 Dec 22 2024 12:15:11
%S A209190 1,2,3,2,5,2,7,2,3,1,11,3,31,41,3,61,71,3,7,2,2,2,2,2,2,2,2,2,2,3,13,
%T A209190 23,3,43,53,3,73,83,3,2,2,2,2,2,2,2,2,2,2,5,3,5,5,3,5,5,3,5,5,2,2,2,2,
%U A209190 2,2,2,2,2,2,7,17,3,37,47,3,67,7,3,97,2,2,2
%N A209190 Least prime factor of reversal of digits of n.
%C A209190 This is to lpf (A020639) as A210437 is to gpf (A006530). - _Jonathan Vos Post_, Mar 22 2012
%H A209190 Alois P. Heinz, <a href="/A209190/b209190.txt">Table of n, a(n) for n = 1..12000</a>
%H A209190 PrimeFan, <a href="http://primefan.tripod.com/EsotericIntegerSequences.html">Listing of Esoteric Integer Sequences</a>
%H A209190 PrimeFan, <a href="/A031214/a031214.pdf">Esoteric Integer Sequences</a> [Cached copy]
%F A209190 a(n) = A020639(A004086(n)) = lpf(R(n)). - _Jonathan Vos Post_, Mar 22 2012
%p A209190 read("transforms") ;
%p A209190 A209190 := proc(n)
%p A209190 A020639(digrev(n)) ;
%p A209190 end proc:
%p A209190 seq(A209190(n),n=1..100) ; # _R. J. Mathar_, Mar 22 2012
%t A209190 a[n_] := FactorInteger[IntegerReverse[n]][[1, 1]];
%t A209190 Array[a, 100] (* _Jean-François Alcover_, Jan 14 2021 *)
%o A209190 (PARI) lpf(n) = if (n==1, 1, vecmin(factor(n)[,1]));
%o A209190 a(n) = lpf(fromdigits(Vecrev(digits(n)))); \\ _Michel Marcus_, Feb 11 2020
%Y A209190 Cf. A004086, A020639, A210437.
%K A209190 nonn,base,look
%O A209190 1,2
%A A209190 _N. J. A. Sloane_, Mar 05 2012