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a(n) is the least divisor u of A331219(n) such that the binary representations of u and of A331219(n)/u have the same number of 0's and the same number of 1's.
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%I #11 Jan 13 2020 18:26:41

%S 1,2,3,4,5,5,6,7,8,9,9,10,9,10,11,11,12,11,13,13,14,15,16,17,17,18,17,

%T 18,19,19,20,17,19,18,21,21,19,20,22,19,21,23,19,21,22,22,24,21,22,23,

%U 25,25,23,26,23,25,26,27,27,28,27,29,29,30,31,32,33,33

%N a(n) is the least divisor u of A331219(n) such that the binary representations of u and of A331219(n)/u have the same number of 0's and the same number of 1's.

%H Rémy Sigrist, <a href="/A331266/b331266.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) * A331267(n) = A331219(n).

%o (PARI) b=2; k=68; for (n=1, oo, fordiv (n, u, if (vecsort(digits(u,b))==vecsort(digits(n/u,b)), print1 (u", "); break (if (k--, 1, 2)))))

%Y Cf. A331219, A331267.

%K nonn,base

%O 1,2

%A _Rémy Sigrist_, Jan 13 2020