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Search: id:A131568
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| A131568 |
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a(n)=sum in base 10 of numbers which in base 2 contain exactly n digits 1 and not more than n digits 0. |
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+0
1
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OFFSET
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0,2
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FORMULA
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a(n) = (2*n)!*(2^(2^n)-1)/(2*n!*n!)
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EXAMPLE
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For n=2 (11)b2 = (3)b10 (101)b2=(5)b10 (110)b2=(6)b10 (1100)b2=(12)b10 (1010)b2=(10)b10 (1001)b2=(9)b10 then a(2)=3+5+6+12+10+9=45
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CROSSREFS
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Adjacent sequences: A131565 A131566 A131567 this_sequence A131569 A131570 A131571
Sequence in context: A060242 A141445 A076140 this_sequence A124487 A132303 A008931
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KEYWORD
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easy,nonn
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AUTHOR
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Philippe LALLOUET (philip.lallouet(AT)wanadoo.fr), Aug 27 2007
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