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A125910
a(n) is the number of nonnegative integers k less than 10^n such that the decimal representation of k lacks the digit 1, at least one of digits 2,3,4 and at least one of digits 5,6,7,8,9.
11
9, 81, 723, 6381, 55539, 475461, 3993243, 32857101, 264890019, 2094889941, 16282118763, 124625344221, 941303216499, 7029057066021, 51980086628283, 381227207181741, 2776407821318979, 20100192515299701, 144786930345697803, 1038495372200033661
OFFSET
1,1
FORMULA
a(n) = 15*7^n-45*6^n+65*5^n-55*4^n+28*3^n-8*2^n+1.
G.f.: -3*x*(1680*x^6 -3976*x^5 +3946*x^4 -1807*x^3 +451*x^2 -57*x+3) / ((x -1)*(2*x -1)*(3*x -1)*(4*x -1)*(5*x -1)*(6*x -1)*(7*x -1)). - Colin Barker, Feb 22 2015
EXAMPLE
a(8) = 32857101.
MAPLE
f:=n->15*7^n-45*6^n+65*5^n-55*4^n+28*3^n-8*2^n+1;
PROG
(PARI) Vec(-3*x*(1680*x^6 -3976*x^5 +3946*x^4 -1807*x^3 +451*x^2 -57*x+3) / ((x -1)*(2*x -1)*(3*x -1)*(4*x -1)*(5*x -1)*(6*x -1)*(7*x -1)) + O(x^100)) \\ Colin Barker, Feb 22 2015
CROSSREFS
Cf. A125630.
Sequence in context: A206857 A073531 A206694 * A171283 A174108 A254435
KEYWORD
nonn,base,easy
AUTHOR
Aleksandar M. Janjic and Milan Janjic, Feb 04 2007
STATUS
approved