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 A368823 #11 Jan 07 2024 09:44:53 %S A368823 1,2,6,3,15,10,70,35,35,14,154,231,3003,858,1430,715,12155,24310, %T A368823 461890,46189,969969,176358,4056234,676039,676039,104006,104006,7429, %U A368823 215441,6463230,200360130,100180065,367326905,43214930,60500902,30250451,1119266687,117817546,4594884294,11487210735 %N A368823 a(1) = 1; for n > 1, a(n) = A055231(a(n-1) * n), where A055231(k) is the powerfree part of k. %C A368823 Terms are squarefree. - _Michael De Vlieger_, Jan 07 2024. %e A368823 a(4) = 3 as a(3)*4 = 6*4 = 24 = 2*2*2*3, and the powerfree part of 24 is 3. %t A368823 f[x_] := Times @@ Map[#1^(#2 Boole[#2 == 1]) & @@ # &, FactorInteger[x]]; a[n_] := f[n* a[n - 1]]; a[1] = 1; Array[a, 120] (* _Michael De Vlieger_, Jan 07 2024 *) %Y A368823 Cf. A368825 (addition), A055231, A005117, A124010. %K A368823 nonn %O A368823 1,2 %A A368823 _Scott R. Shannon_, Jan 07 2024