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A331662 Odd composite numbers k such that the divisors of the binary reversal of k (A030101) are the binary reversals of the divisors of k. 3

%I

%S 9,15,21,27,45,51,63,85,93,95,111,119,123,125,153,187,189,219,221,255,

%T 335,365,381,485,511,597,629,655,681,697,765,771,831,965,1011,1139,

%U 1241,1285,1389,1461,1533,1535,1563,1649,1731,1791,1799,1983,2031,2043,2045

%N Odd composite numbers k such that the divisors of the binary reversal of k (A030101) are the binary reversals of the divisors of k.

%H Amiram Eldar, <a href="/A331662/b331662.txt">Table of n, a(n) for n = 1..10000</a>

%e 9 is a term since the binary representations of its divisors, 1, 3 and 9, are palindromic: 1, 11 and 1001, i.e., the binary reversals of themselves.

%e 95 is a term since the binary representations of its divisors, 1, 5, 19 and 95, are 1, 101, 10011 and 1011111, and their binary reversals, 1, 101, 11001, 1111101, or 1, 5, 25 and 125 in decimal representation, are the divisors of 125, which is the binary reversal of 95.

%t Select[Range[1, 2000, 2], CompositeQ[#] && (Divisors @ IntegerReverse[#, 2]) == IntegerReverse[Divisors[#], 2] &]

%Y Cf. A030101.

%Y A329419, A331663 and A331664 are subsequences.

%K nonn,base

%O 1,1

%A _Amiram Eldar_, Jan 23 2020

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Last modified October 16 23:07 EDT 2021. Contains 348047 sequences. (Running on oeis4.)