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 A334132 #34 Jan 31 2023 20:46:25 %S A334132 1,11,3,7,11,312211,13112221,11,5581,26966089,7,20328937,29,3,3,3, %T A334132 1637,103,50593,43,13,19,17,103,31,19,7,3,19,1208033,23,3,3,83,3,233, %U A334132 3,3 %N A334132 Smallest prime factor of n-th term in Look and Say sequence A005150, with a(1)=1. %C A334132 The terms in A005150 that are known to be primes are a(2) = 11, a(6) = 312211 and a(7) = 13112221 (A100108). %C A334132 a(n) = 3 iff A004977(n) is positive and divisible by 3. %C A334132 a(39) > 2*10^9. a(62) > 10^7. - _Tyler Busby_, Jan 25 2023 %H A334132 Tyler Busby, <a href="/A334132/a334132.txt">Table of n, a(n) for n = 1..75 with -1 for those entries where a(n) has not yet been found</a>, Jan 25 2023. %H A334132 Wikipedia, <a href="http://en.wikipedia.org/wiki/Look-and-say_sequence">Look-and-say sequence</a> %F A334132 a(n) = A020639(A005150(n)). %e A334132 A005150(7) = 13112221 is prime and a(7) = 13112221. %e A334132 A005150(9) = 31131211131221 = 5581 * 5578070441, hence a(9) = 5581. %Y A334132 Cf. A004977 (sum of digits of terms of A005150), A005150 (Look and Say sequence), A020639, A079562, A100108 (primes in A005150). %K A334132 nonn,base,more %O A334132 1,2 %A A334132 _Bernard Schott_, Apr 15 2020 %E A334132 a(17)-a(38) from _Jinyuan Wang_, Apr 15 2020