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 A280684 #14 Sep 08 2022 08:46:18 %S A280684 1,2,2,4,2,9,2,7,4,9,2,28,2,9,9,11,2,28,2,28,9,9,2,65,4,9,7,28,2,125, %T A280684 2,16,9,9,9,100,2,9,9,65,2,125,2,28,28,9,2,126,4,28,9,28,2,65,9,65,9, %U A280684 9,2,637,2,9,28,22,9,125,2,28,9,125,2,247,2,9,28 %N A280684 a(n) = number of divisors of the product of the divisors of n. %H A280684 Antti Karttunen, <a href="/A280684/b280684.txt">Table of n, a(n) for n = 1..10000</a> %F A280684 a(n) = A000005(A007955(n)). %F A280684 a(p) = 2 for p = primes (A000040). %F A280684 a(n) = 4 for squares of primes (A001248). %F A280684 a(n) = n for numbers 1, 2, 4, 28, 100, ... %F A280684 a(n) = tau(n) for noncomposites (A008578). %F A280684 a(n) = a(n+1) for numbers in A052213. %e A280684 For n = 4; a(n) = tau (1*2*4) = tau(8) = 4. %o A280684 (Magma) [#[d: d in Divisors(&*[d: d in Divisors(n)])]: n in [1..100]] %o A280684 (PARI) %o A280684 A007955(n) = if(issquare(n, &n), n^numdiv(n^2), n^(numdiv(n)/2)); \\ This function from _Charles R Greathouse IV_, Feb 11 2011 %o A280684 A280684(n) = numdiv(A007955(n)); \\ _Antti Karttunen_, May 19 2017 %Y A280684 Cf. A000005, A000040, A001248, A007955, A008578, A052213, A280685, A280582. %K A280684 nonn %O A280684 1,2 %A A280684 _Jaroslav Krizek_, Jan 07 2017