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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

Colin Barker, Table of n, a(n) for n = 1..1000

Milan Janjic, Enumerative Formulas for Some Functions on Finite Sets

Index entries for linear recurrences with constant coefficients, signature (15,-85,225,-274,120).

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

Cf. A125630, A125948, A125947, A125946, A125945, A125940, A125909, A125908, A125880, A125897, A125904, A125858.

Sequence in context: A267230 A188868 A267469 * A268942 A269638 A269535

Adjacent sequences:  A126636 A126637 A126638 * A126640 A126641 A126642

KEYWORD

nonn,base,easy

AUTHOR

Aleksandar M. Janjic and Milan Janjic, Feb 08 2007

STATUS

approved

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Last modified June 13 00:57 EDT 2021. Contains 344980 sequences. (Running on oeis4.)