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A126639
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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 digit 1,2,3, at least one of digits 4,5,6 and at least one of digits 7,8,9.
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3
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7, 49, 331, 2137, 13147, 77449, 440251, 2432857, 13151707, 69895849, 366600571, 1903222777, 9802234267, 50171448649, 255545887291, 1296626911897, 6559153748827, 33101134543849, 166731005404411, 838567970940217, 4212526479343387, 21141483461069449
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OFFSET
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1,1
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LINKS
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FORMULA
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a(n) = 9*5^n-18*4^n+15*3^n-6*2^n+1.
G.f.: -x*(120*x^4-238*x^3+191*x^2-56*x+7) / ((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(5*x-1)). - Colin Barker, Feb 22 2015
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MAPLE
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f:=n->9*5^n-18*4^n+15*3^n-6*2^n+1;
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MATHEMATICA
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LinearRecurrence[{15, -85, 225, -274, 120}, {7, 49, 331, 2137, 13147}, 30] (* Harvey P. Dale, Aug 12 2015 *)
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PROG
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(PARI) Vec(-x*(120*x^4-238*x^3+191*x^2-56*x+7) / ((x-1)*(2*x-1)*(3*x-1)*(4*x-1)*(5*x-1)) + O(x^100)) \\ Colin Barker, Feb 22 2015
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CROSSREFS
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Cf. A125630, A125948, A125947, A125946, A125945, A125940, A125909, A125908, A125880, A125897, A125904, A125858.
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KEYWORD
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nonn,base,easy
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AUTHOR
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STATUS
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approved
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