Search: id:A055842
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%I A055842
%S A055842 1,3,16,80,400,2000,10000,50000,250000,1250000,6250000,31250000,
%T A055842 156250000,781250000,3906250000,19531250000,97656250000,488281250000,
%U A055842 2441406250000
%N A055842 A second order recursive sequence.
%C A055842 First differences of A005054.
%C A055842 For n>=2, a(n) is equal to the number of functions f:{1,2,...,n}->{1,
               2,3,4,5} 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} we have f(x_1)<>y_1 and f(x_2)<> y_2. 
               - Milan R. Janjic (agnus(AT)blic.net), Apr 19 2007
%D A055842 A. H. Beiler, Recreations in the Theory of Numbers, Dover, N.Y., 1964, 
               pps. 194-196.
%H A055842 Milan Janjic, <a href="http://www.pmfbl.org/janjic/">Enumerative Formulas 
               for Some Functions on Finite Sets</a>
%F A055842 a(n)=16*5^(n-2), a(0)=1, a(1)=3.
%e A055842 a(n)=5a(n-1)+[(-1)^n]*C(2,2-n). G.f.(x)=(1-x)^2/(1-5x).
%Y A055842 Cf. A000351 and A005054.
%Y A055842 Sequence in context: A003769 A005386 A053572 this_sequence A037773 A037661 
               A072615
%Y A055842 Adjacent sequences: A055839 A055840 A055841 this_sequence A055843 A055844 
               A055845
%K A055842 easy,nonn
%O A055842 0,2
%A A055842 Barry E. Williams, May 30 2000

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