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 A309002 #13 Jul 07 2019 13:09:07 %S A309002 1,4,9,16,25,36,49,512,81,100,121,144,169,196,225,65536,289,324,361, %T A309002 400,441,484,529,4608,625,676,19683,784,841,900,961,33554432,1089, %U A309002 1156,1225,1296,1369,1444,1521,12800,1681,1764,1849,1936,2025,2116,2209,589824 %N A309002 Multiplicative with a(p) = p^2 and a(p^e) = p^a(e) for any e > 1 and prime number p. %C A309002 To compute a(n): square every prime number at leaf position in the prime tower factorization of n (the prime tower factorization of a number is defined in A182318). %C A309002 For any n > 0, a(n) is the least k such that A308993(k) = n. %H A309002 Rémy Sigrist, <a href="/A309002/b309002.txt">Table of n, a(n) for n = 1..10000</a> %H A309002 Rémy Sigrist, <a href="/A309002/a309002.pdf">Illustration of first terms</a> %F A309002 A308993(a(n)) = n. %F A309002 A185102(a(n)) = 1 + A185102(n) for any n > 1. %F A309002 a(n) >= n^2 with equality iff n is cubefree (A004709). %e A309002 See Links section. %o A309002 (PARI) a(n) = my (f=factor(n)); prod (i=1, #f~, f[i, 1]^if (f[i, 2]==1, 2, a(f[i, 2]))) %Y A309002 Cf. A004709, A182318, A185102, A308993. %K A309002 nonn,mult %O A309002 1,2 %A A309002 _Rémy Sigrist_, Jul 05 2019