%I A056002
%S A056002 1,9,100,1100,12100,133100,1464100,16105100,177156100,1948717100,
%T A056002 21435888100,235794769100,2593742460100,28531167061100,313842837672100,
%U A056002 3452271214393100,37974983358324100,417724816941565100
%N A056002 a(n)=[(10)^2]*11^(n-2); a(0)=1, a(1)=9.
%C A056002 For n>=2, a(n) is equal to the number of functions f:{1,2,...,n}->{1,
               2,3,4,5,6,7,8,9,10,11} such that for fixed, different x_1, x_2 in 
               {1,2,...,n} and fixed y_1, y_2 in {1,2,3,4,5,6,7,8,9,10,11} we have 
               f(x_1)<>y_1 and f(x_2)<> y_2. - Milan R. Janjic (agnus(AT)blic.net), 
               Apr 19 2007
%D A056002 A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, 
               pps. 194-196.
%H A056002 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas 
               for Some Functions on Finite Sets</a>
%F A056002 a(n)=11a(n-1)+[(-1)^n]*C(2, 2-n). G.f.(x)=(1-x)^2/(1-11x).
%Y A056002 Cf. A001020.
%Y A056002 Sequence in context: A027769 A065736 A092936 this_sequence A060150 A103461 
               A101563
%Y A056002 Adjacent sequences: A055999 A056000 A056001 this_sequence A056003 A056004 
               A056005
%K A056002 easy,nonn
%O A056002 0,2
%A A056002 Barry E. Williams, Jun 18 2000
%E A056002 More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jul 04 2000