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A126639 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. 3
7, 49, 331, 2137, 13147, 77449, 440251, 2432857, 13151707, 69895849, 366600571, 1903222777, 9802234267, 50171448649, 255545887291, 1296626911897, 6559153748827, 33101134543849, 166731005404411, 838567970940217, 4212526479343387, 21141483461069449 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
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
MAPLE
f:=n->9*5^n-18*4^n+15*3^n-6*2^n+1;
MATHEMATICA
LinearRecurrence[{15, -85, 225, -274, 120}, {7, 49, 331, 2137, 13147}, 30] (* Harvey P. Dale, Aug 12 2015 *)
PROG
(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
CROSSREFS
Sequence in context: A267230 A188868 A267469 * A268942 A269638 A269535
KEYWORD
nonn,base,easy
AUTHOR
Aleksandar M. Janjic and Milan Janjic, Feb 08 2007
STATUS
approved

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Last modified March 29 00:26 EDT 2024. Contains 371264 sequences. (Running on oeis4.)