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 A361631 #14 Mar 23 2023 23:09:03 %S A361631 1,1,1,1,2,1,1,1,2,1,2,1,2,1,1,1,2,1,2,1,2,1,2,1,2,1,2,1,1,1,1,1,2,1, %T A361631 2,1,2,1,2,1,1,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,2,1,1,1,2,1,1,1,1,1,2,1, %U A361631 1,1,2,1,2,1,2,1,1,1,2,1,2,1,1,1,2,1,2,1 %N A361631 a(n) is the denominator of the median of the distinct prime factors of n. %H A361631 Winston de Greef, <a href="/A361631/b361631.txt">Table of n, a(n) for n = 2..10000</a> %F A361631 For p a prime, a(p^k) = 1. %e A361631 a(12) = 2 since the distinct prime factors of 12 are 2 and 3, of median equal to 5/2. %e A361631 a(30) = 1 since the distinct prime factors of 30 are 2, 3, and 5, of median equal to 3. %t A361631 a[n_]:=Denominator[Median[FactorInteger[n][[All, 1]]]]; Array[a,88,2] %o A361631 (PARI) a(n)=my(f=factor(n)[,1]~, i=length(f)); denominator(if(i%2, f[i\2+1], (f[i/2]+f[i/2+1])/2)) \\ _Winston de Greef_, Mar 23 2023 %Y A361631 Cf. A001221, A027748, A323172, A361566, A361630 (numerator), A361633 (with multiplicity). %K A361631 nonn,frac %O A361631 2,5 %A A361631 _Stefano Spezia_, Mar 18 2023