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 A261411 #16 Jul 09 2025 04:40:07 %S A261411 1,11,3,11,41,3,239,11,3,11,11,3,11,11,3,11,11,3,71,21557,19,17,31, %T A261411 181,17,353,19,31,19,29,17,29,11616377,214141,19,5471,17,13883,3,7, %U A261411 421219193,3,17,7,3,7,101,3,634324033999,13,19,13,83,13,23,13,19,13,19 %N A261411 a(1)=1; thereafter a(n) = smallest prime factor of A261570(n). %H A261411 David Broadhurst and Hiroaki Yamanouchi, <a href="/A261411/b261411.txt">Table of n, a(n) for n = 1..99</a> (First 61 terms from Hiroaki Yamanouchi) %e A261411 A261570(11) = 12345678911987654321 = (11)(59)(34631)(43117)(6373)(1999), so a(10) = 11. %e A261411 Note that a(2007) = A261570(2007) is a 21233-digit (probable) prime. %Y A261411 Cf. A261570, A067063, A075023. %K A261411 nonn %O A261411 1,2 %A A261411 _N. J. A. Sloane_, Aug 24 2015, based on _Robert G. Wilson v_'s comment in A261570 %E A261411 a(41)-a(59) from _Hiroaki Yamanouchi_, Aug 24 2015