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Search: id:A117067
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| A117067 |
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Decimal value of binary number whose n-th 1 is followed by F(n) 0's. |
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+0
2
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| 5, 21, 169, 2705, 173121, 88637953, 1452244221953, 6091153749114355713, 209290449178831574011566096385, 15080966222943833716372357571365139853460111361
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OFFSET
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0,1
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COMMENT
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a(1) = 5 is prime; a(6) = 88637953 is prime.
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FORMULA
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a(n) = SUM[i=1,n] 2^(1+F(i)) where F(i) = A000045(i). a(n) = SUM[i=1,n] 2^nint((phi^(n+1))/sqrt(5)).
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EXAMPLE
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a(1) = 5 because 101 (base 2) = 5 (base 10).
a(2) = 21 because 10101 (base 2) = 21 (base 10).
a(3) = 169 because 10101001 (base 2) = 169 (base 10).
a(4) = 2705 because 101010010001 (base 2) = 2705 (base 10).
a(5) = 173121 because 101010010001000001 (base 2) = 173121 (base 10).
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CROSSREFS
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Cf. A000040, A000045.
Sequence in context: A002711 A124311 A050910 this_sequence A123334 A140196 A027160
Adjacent sequences: A117064 A117065 A117066 this_sequence A117068 A117069 A117070
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KEYWORD
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base,easy,nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com), Apr 16 2006
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