A331588 -id:A331588 - cp's OEIS frontend

A331587 Odd numbers of the form k * reverse(k) (where reverse(k) is the binary reversal of k, A030101(k)).

1, 9, 25, 49, 81, 143, 225, 289, 441, 475, 667, 729, 961, 1089, 1517, 1715, 2025, 2223, 2279, 2601, 2867, 3245, 3969, 4225, 5329, 5589, 6499, 6853, 7225, 7875, 8023, 8383, 8649, 9559, 9801, 9919, 10179, 11449, 11845, 11875, 13653, 14161, 16129, 16641, 19865

Offset: 1

Rémy Sigrist, Jan 21 2020

A192775 is a subsequence.

			The binary representations of 11 and of 13 are "1011" and "1101", respectively, so 11*13 = 143 belongs to the sequence.

Rémy Sigrist, Table of n, a(n) for n = 1..8347

Cf. A030101, A092213, A192775, A331588, A331589.

is(n) = if (n%2, fordiv (n, d, if (d*fromdigits(Vecrev(binary(d)),2)==n, return (1)))); return (0)

A331589 a(n) is the greatest k such that A331587(n) = k * reverse(k) (where reverse(k) is the binary reversal of k, A030101(k)).

Original entry on oeis.org

1, 3, 5, 7, 9, 13, 15, 17, 21, 25, 29, 27, 31, 33, 41, 49, 45, 57, 53, 51, 61, 59, 63, 65, 73, 81, 97, 89, 85, 105, 113, 101, 93, 121, 99, 109, 117, 107, 115, 125, 123, 119, 127, 129, 145, 161, 153, 177, 169, 193, 165, 185, 209, 201, 225, 181, 197, 217, 241

Offset: 1

Rémy Sigrist, Jan 21 2020

Rémy Sigrist, Table of n, a(n) for n = 1..8347
Rémy Sigrist, PARI program for A331589

Cf. A030101, A331587, A331588.

PARI
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See Links section.
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a(n) = A030101(A331588(n)).

a(n) * A331588(n) = A331587(n).

cp's OEIS Frontend

A331587 Odd numbers of the form k * reverse(k) (where reverse(k) is the binary reversal of k, A030101(k)).

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