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Search: id:A135650
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| A135650 |
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Even perfect numbers written in base 2. |
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+0
10
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| 110, 11100, 111110000, 1111111000000, 1111111111111000000000000, 111111111111111110000000000000000, 1111111111111111111000000000000000000
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The number of digits of a(n) is equal to 2*A000043(n)-1. The central digit is "1". The first digits are "1". The last digits are "0". The number of digits "1" is equal A000043(n). The number of digits "0" is equal A000043(n)-1.
The concatenation of digits "1" of a(n) gives the n-th Mersenne prime written in binary (see A117293(n)).
Also, the number of digits of a(n) is equal to A133033(n), the number of proper divisors of n-th even perfect number.
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LINKS
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O. E. Pol, Determinacion geometrica de los numeros primos y perfectos.
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EXAMPLE
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a(3)=111110000 because the 3rd. even perfect number is 496 and 496 written in base 2 is 111110000. Note that 11111 is the 3rd. Mersenne prime A000668(3)=31 written in base 2.
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CROSSREFS
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Cf. A000043, A000396, A000668, A090748, A117293.
Cf. A061645, A133033.
Sequence in context: A058935 A109241 A090490 this_sequence A097580 A139478 A143750
Adjacent sequences: A135647 A135648 A135649 this_sequence A135651 A135652 A135653
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KEYWORD
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base,nonn
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AUTHOR
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Omar E. Pol (info(AT)polprimos.com), Feb 21 2008, Feb 22 2008, Apr 28 2009
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