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 A326620 #9 Jan 28 2025 16:54:50
%S A326620 1,1,1,1,2,1,1,1,1,1,2,1,2,2,1,1,2,1,1,1,1,1,2,1,2,1,2,1,1,1,1,2,1,2,
%T A326620 2,1,2,1,1,1,3,1,1,2,1,1,2,1,1,2,2,1,2,1,2,1,2,1,1,1,1,1,1,2,3,1,1,2,
%U A326620 3,1,2,1,2,2,2,2,1,1,1,1,1,1,3,1,2,1,1,1,1,1,1,2,1,2,2,1,2,2,1,1,3,1,2,1
%N A326620 Denominator of the average of the set of distinct prime indices of n.
%C A326620 A prime index of n is a number m such that prime(m) divides n. The multiset of prime indices of n is row n of A112798.
%H A326620 Antti Karttunen, <a href="/A326620/b326620.txt">Table of n, a(n) for n = 2..65537</a>
%H A326620 <a href="/index/Pri#prime_indices">Index entries for sequences related to prime indices in the factorization of n</a>.
%e A326620 The distinct prime indices of 12 are {1,2}, with average 3/2, so a(12) = 2.
%e A326620 The sequence of fractions begins: 1, 2, 1, 3, 3/2, 4, 1, 2, 2, 5, 3/2, 6, 5/2, 5/2, 1, 7, 3/2, 8, 2, 3, 3, 9, 3/2, 3, 7/2, 2, 5/2, 10, 2.
%t A326620 Table[Denominator[Mean[PrimePi/@First/@FactorInteger[n]]],{n,2,100}]
%o A326620 (PARI) A326620(n) = if(1==n,0,denominator(vecsum(apply(primepi,factor(n)[,1]))/omega(n))); \\ _Antti Karttunen_, Jan 28 2025
%Y A326620 Positions of 1's are A326621.
%Y A326620 The average of the multiset of prime indices is A326567/A326568.
%Y A326620 The average of the multiset of prime factors is A123528/A123529.
%Y A326620 The average of the set of distinct prime indices is A326619/A326620.
%Y A326620 The average of the set of distinct prime factors is A323171/A323172.
%Y A326620 Cf. A001221, A067629, A078174, A078175, A112798, A316413.
%K A326620 nonn,frac
%O A326620 2,5
%A A326620 _Gus Wiseman_, Jul 14 2019
%E A326620 Data section extended to a(105) by _Antti Karttunen_, Jan 28 2025