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A331219
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Positive numbers of the form u * v where the binary representations of u and of v have the same number of 0's and the same number of 1's.
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5
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1, 4, 9, 16, 25, 30, 36, 49, 64, 81, 90, 100, 108, 120, 121, 143, 144, 154, 169, 182, 196, 225, 256, 289, 306, 324, 340, 360, 361, 399, 400, 408, 418, 432, 441, 462, 475, 480, 484, 494, 525, 529, 532, 546, 550, 572, 576, 588, 616, 621, 625, 650, 667, 676, 690
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OFFSET
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1,2
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COMMENTS
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In other words, the terms of this sequence are squares or the products of two binary anagrams.
Leading zeros are ignored.
If m belongs to the sequence, then 4*m also belongs to the sequence.
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LINKS
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FORMULA
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EXAMPLE
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The binary representations of 5 and 6 are "101" and "110", respectively.
So 5 and 6 are binary anagrams, and 30 = 5*6 belongs to the sequence.
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PROG
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(PARI) is(n, base=2) = fordiv (n, d, if (vecsort(digits(d, base))==vecsort(digits(n/d, base)), return (1))); return (0)
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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