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A330681 a(n) = A283980(A025487(n)).

%I A330681 #13 Dec 26 2019 15:43:58
%S A330681 1,6,36,30,216,180,1296,1080,210,7776,900,6480,1260,46656,5400,38880,
%T A330681 7560,279936,32400,6300,233280,2310,27000,45360,1679616,194400,37800,
%U A330681 1399680,13860,162000,272160,10077696,1166400,226800,8398080,83160,972000,44100,1632960,60466176,189000,6998400,69300,810000,1360800
%N A330681 a(n) = A283980(A025487(n)).
%C A330681 After 1, contains only the least representatives of such prime signatures where the maximal exponent occurs more than once. However, here the terms are not in ascending order.
%H A330681 Antti Karttunen, <a href="/A330681/b330681.txt">Table of n, a(n) for n = 1..15703</a>
%F A330681 a(n) = A283980(A025487(n)).
%F A330681 A046523(a(n)) = a(n).
%F A330681 A085089(a(n)) = A101296(a(n)) = A330683(n).
%e A330681 For example, 180 = 2^2 * 3^2 * 5^1 is present, because the maximal exponent in its prime factorization is 2, which occurs as an exponent of both 2 and 3, and because 180 is the minimal representative of the prime signature (2,2,1), as A046523(180) = 180.
%o A330681 (PARI)
%o A330681 A283980(n) = {my(f=factor(n)); prod(i=1, #f~, my(p=f[i, 1], e=f[i, 2]); if(p==2, 6, nextprime(p+1))^e)}; \\ From A283980
%o A330681 A025487list(e) = { my(lista = List([1, 2]), i=2, u = 2^e, t); while(lista[i] != u, if(2*lista[i] <= u, listput(lista,2*lista[i]); t = A283980(lista[i]); if(t <= u, listput(lista,t))); i++); vecsort(Vec(lista)); }; \\ Returns a list of terms up to the term 2^e.
%o A330681 v025487 = A025487list(64);
%o A330681 A025487(n) = v025487[n];
%o A330681 A330681(n) = A283980(A025487(n));
%Y A330681 Cf. A025487, A046523, A283980, A329899, A330683.
%K A330681 nonn
%O A330681 1,2
%A A330681 _Antti Karttunen_, Dec 26 2019