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Search: id:A036537
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| A036537 |
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Numbers n such that number of divisors of n is a power of 2. |
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+0
5
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| 1, 2, 3, 5, 6, 7, 8, 10, 11, 13, 14, 15, 17, 19, 21, 22, 23, 24, 26, 27, 29, 30, 31, 33, 34, 35, 37, 38, 39, 40, 41, 42, 43, 46, 47, 51, 53, 54, 55, 56, 57, 58, 59, 61, 62, 65, 66, 67, 69, 70, 71, 73, 74, 77, 78, 79, 82, 83, 85, 86, 87, 88, 89, 91, 93, 94, 95, 97, 101, 102
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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Primes and A030513(d[ x ]=4) are subsets; d[ 16k+4 ] and d[ 16k+12 ] have form of 3Q, so x=16k+4 or 16k-4 numbers are missing
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FORMULA
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bi[ x_ ] := 1-Sign[ N[ Log[ 2, x ], 5 ]-Floor[ N[ Log[ 2, x ], 5 ] ] ]; ld[ x_ ] := Length[ Divisors[ x ] ]; Flatten[ Position[ Table[ bi[ ld[ x ] ], {x, 1, m} ], 1 ] ]
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EXAMPLE
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383,384,385,386 have 1,16,8,4 divisors so are successive integers and consecutive terms of this seuence.
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CROSSREFS
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A000005, A030513, A036537.
Adjacent sequences: A036534 A036535 A036536 this_sequence A036538 A036539 A036540
Sequence in context: A109423 A028801 A002035 this_sequence A072510 A084116 A137620
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu)
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