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 A366441 #12 Oct 10 2023 16:25:34
%S A366441 1,2,2,2,2,2,2,2,3,2,2,4,2,2,2,2,3,2,4,2,2,4,2,2,2,4,2,2,4,2,4,4,2,2,
%T A366441 2,2,2,2,4,4,3,4,2,2,4,2,2,4,4,2,2,4,2,4,2,2,3,2,6,2,2,4,4,2,2,2,2,4,
%U A366441 4,4,2,4,4,4,2,2,2,2,4,2,2,6,4,2,4,2,4
%N A366441 The number of divisors of the 5-rough numbers (A007310).
%H A366441 Amiram Eldar, <a href="/A366441/b366441.txt">Table of n, a(n) for n = 1..10000</a>
%F A366441 a(n) = A000005(A007310(n)).
%F A366441 Sum_{k=1..n} a(k) ~ (log(n) + 2*gamma - 1 + 2*log(6)) * n / 3, where gamma is Euler's constant (A001620).
%t A366441 a[n_] := DivisorSigma[0, 2*Floor[3*n/2] - 1]; Array[a, 100]
%o A366441 (PARI) a(n) = numdiv((3*n)\2 << 1 - 1)
%o A366441 (Python)
%o A366441 from sympy import divisor_count
%o A366441 def A366441(n): return divisor_count((n+(n>>1)<<1)-1) # _Chai Wah Wu_, Oct 10 2023
%Y A366441 Cf. A000005, A001620, A007310, A366442.
%Y A366441 Similar sequences: A048691, A072048, A076400, A099774, A358040, A363194, A363195.
%K A366441 nonn,easy
%O A366441 1,2
%A A366441 _Amiram Eldar_, Oct 10 2023