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A126645
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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 and 5, at least one of digits 6,7 and at least one of digits 8,9.
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1
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5, 21, 77, 261, 845, 2661, 8237, 25221, 76685, 232101, 700397, 2109381, 6344525, 19066341, 57264557, 171924741, 516036365, 1548633381, 4646948717, 13942943301, 41833024205, 125507461221, 376539160877, 1129651037061
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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LINKS
| Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets
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FORMULA
| a(n)=4*3^n-4*2^n+1
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EXAMPLE
| a(8)=25221
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MAPLE
| f:=n->4*3^n-4*2^n+1;
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CROSSREFS
| Cf. A125630, A125948, A125947, A125946, A125945, A125940, A125909, A125908, A125880, A125897, A125904, A125858.
Sequence in context: A201435 A202507 A079923 * A026329 A014533 A134770
Adjacent sequences: A126642 A126643 A126644 * A126646 A126647 A126648
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KEYWORD
| nonn,base
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AUTHOR
| Aleksandar M. Janjic and Milan R. Janjic (agnus(AT)blic.net), Feb 08 2007
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