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Search: id:A126646
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| A126646 |
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a(n) is the number of integers k less than 10^n such that the decimal representation of k lacks the digits 1,2,3,4,5,6 and 7 and at least one of digits 8,9. |
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+0
2
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| 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767, 65535, 131071, 262143, 524287, 1048575, 2097151, 4194303, 8388607, 16777215, 33554431, 67108863, 134217727, 268435455, 536870911, 1073741823, 2147483647
(list; graph; listen)
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OFFSET
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1,1
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LINKS
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Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
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FORMULA
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a(n)=2*2^n-1
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EXAMPLE
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a(8)=511
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MAPLE
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f:=n->2*2^n-1;
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CROSSREFS
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Cf. A125630, A125948, A125947, A125946, A125945, A125940, A125909, A125908, A125880, A125897, A125904, A125858.
Sequence in context: A043764 A097002 A060152 this_sequence A000225 A123121 A117060
Adjacent sequences: A126643 A126644 A126645 this_sequence A126647 A126648 A126649
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KEYWORD
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nonn
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AUTHOR
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Aleksandar M. Janjic and Milan R. Janjic (agnus(AT)blic.net), Feb 08 2007, Feb 13 2007
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