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A125909
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 the digits 2,3 and at least one of digits 4,5,6,7,8,9.
19
9, 79, 681, 5791, 48729, 405919, 3340521, 27094111, 216288249, 1699187359, 13147825161, 100334472031, 756309350169, 5639967562399, 41669245538601, 305413957523551, 2223312590034489, 16091187568891039, 115885120813664841, 831075819022712671
OFFSET
1,1
FORMULA
a(n) = 12*7^n-36*6^n+55*5^n-50*4^n+27*3^n-8*2^n+1.
G.f.: -x*(5040*x^6 -11988*x^5 +11944*x^4 -5479*x^3 +1367*x^2 -173*x+9) / ((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
MAPLE
f:=n->12*7^n-36*6^n+55*5^n-50*4^n+27*3^n-8*2^n+1;
PROG
(PARI) Vec(-x*(5040*x^6 -11988*x^5 +11944*x^4 -5479*x^3 +1367*x^2 -173*x+9) / ((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: A198857 A126632 A294344 * A125421 A163445 A190979
KEYWORD
nonn,base,easy
AUTHOR
Aleksandar M. Janjic and Milan Janjic, Feb 04 2007
STATUS
approved