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.

9, 15, 21, 27, 45, 51, 63, 85, 93, 95, 111, 119, 123, 125, 153, 187, 189, 219, 221, 255, 335, 365, 381, 485, 511, 597, 629, 655, 681, 697, 765, 771, 831, 965, 1011, 1139, 1241, 1285, 1389, 1461, 1533, 1535, 1563, 1649, 1731, 1791, 1799, 1983, 2031, 2043, 2045

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Example

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.
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.

Mathematica

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

Crossrefs

Cf. A030101.

A329419, A331663 and A331664 are subsequences.

Sequence in context: A097636 A179384 A225513 * A007962 A061254 A175626

Adjacent sequences: A331659 A331660 A331661 * A331663 A331664 A331665

Keyword

nonn,base

Author

Amiram Eldar, Jan 23 2020

Status

approved