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A117068
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Decimal value of binary number whose n-th 1 is followed by n^2 0's.
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1
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OFFSET
| 1,1
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COMMENTS
| After a(1) = 5, when is a(n) prime?
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FORMULA
| a(n) = SUM[i=1,n] 2^(n+1).
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EXAMPLE
| a(1) = 5 because 101 (base 2) = 5 (base 10).
a(2) = 161 because 10100001 (base 2) = 161 (base 10).
a(3) = 164865 because 101000010000000001 (base 2) = 164865 (base 10).
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CROSSREFS
| Sequence in context: A197310 A085330 A136368 * A185832 A195950 A195951
Adjacent sequences: A117065 A117066 A117067 * A117069 A117070 A117071
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KEYWORD
| base,easy,nonn
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AUTHOR
| Jonathan Vos Post (jvospost3(AT)gmail.com), Apr 16 2006
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