This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A125909 #14 Jun 13 2015 00:52:17 %S A125909 9,79,681,5791,48729,405919,3340521,27094111,216288249,1699187359, %T A125909 13147825161,100334472031,756309350169,5639967562399,41669245538601, %U A125909 305413957523551,2223312590034489,16091187568891039,115885120813664841,831075819022712671 %N 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. %H A125909 Colin Barker, <a href="/A125909/b125909.txt">Table of n, a(n) for n = 1..1000</a> %H A125909 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas for Some Functions on Finite Sets</a> %H A125909 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (28,-322,1960,-6769,13132,-13068,5040). %F A125909 a(n) = 12*7^n-36*6^n+55*5^n-50*4^n+27*3^n-8*2^n+1. %F A125909 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 %p A125909 f:=n->12*7^n-36*6^n+55*5^n-50*4^n+27*3^n-8*2^n+1; %o A125909 (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 %Y A125909 Cf. A125630. %K A125909 nonn,base,easy %O A125909 1,1 %A A125909 Aleksandar M. Janjic and _Milan Janjic_, Feb 04 2007