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A126642 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 and at least one of digits 6,7,8,9. 3
5, 25, 125, 601, 2765, 12265, 52925, 223801, 932525, 3844105, 15722525, 63936601, 258902285, 1045109545, 4209004925, 16921851001, 67945160045, 272554432585, 1092540156125, 4377129999001, 17529432313805, 70180474597225, 280910151192125 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
a(n) = 4*4^n-6*3^n+4*2^n-1.
a(n) = 10*a(n-1)-35*a(n-2)+50*a(n-3)-24*a(n-4). - Colin Barker, Feb 22 2015
G.f.: -x*(24*x^3-50*x^2+25*x-5) / ((x-1)*(2*x-1)*(3*x-1)*(4*x-1)). - Colin Barker, Feb 22 2015
MAPLE
f:=n->4*4^n-6*3^n+4*2^n-1;
PROG
(PARI) Vec(-x*(24*x^3-50*x^2+25*x-5) / ((x-1)*(2*x-1)*(3*x-1)*(4*x-1)) + O(x^100)) \\ Colin Barker, Feb 22 2015
CROSSREFS
Sequence in context: A366323 A267780 A228736 * A269615 A269579 A269431
KEYWORD
nonn,base,easy
AUTHOR
Aleksandar M. Janjic and Milan Janjic, Feb 08 2007
STATUS
approved

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Last modified March 3 00:46 EST 2024. Contains 370499 sequences. (Running on oeis4.)