%I #12 Aug 13 2020 10:11:38
%S 1,2,3,2,5,6,7,6,6,10,11,6,13,14,15,2,17,6,19,10,21,22,23,6,10,26,3,
%T 14,29,30,31,10,33,34,35,6,37,38,39,30,41,42,43,22,30,46,47,6,14,10,
%U 51,26,53,6,55,42,57,58,59,30,61,62,42,6,65,66,67,34,69,70
%N a(n) is the product of the distinct prime numbers appearing in the prime tower factorization of n.
%C The prime tower factorization of a number is defined in A182318.
%C For any n > 0, a(n) is the product of the terms in n-th row of A336964.
%H Rémy Sigrist, <a href="/A336965/b336965.txt">Table of n, a(n) for n = 1..10000</a>
%e A001221(a(n)) = A115588(n) for any n > 1.
%e a(n) = A007947(A279513(n)).
%e a(n) = n iff n is squarefree (A005117).
%o (PARI) a(n) = { my (f=factor(n), v=vecprod(f[,1]~)); for (k=1, #f~, v=lcm(v, a(f[k,2]))); v }
%Y Cf. A001221, A005117, A007947, A115588, A182318, A336964.
%K nonn
%O 1,2
%A _Rémy Sigrist_, Aug 09 2020