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%I #5 Aug 24 2012 10:49:58
%S 0,1,1,1,1,1,2,1,1,2,2,1,1,1,3,3,3,2,2,1,2,2,3,3,3,2,2,4,2,3,5,3,2,3,
%T 3,2,5,4,3,5,2,6,5,1,2,1,6,5,6,4,4,3,2,4,9,9,9,4,4,2,5,2,4,5,5,7,8,6,
%U 5,5,5,7,6,11,7,7,5,5,6,7,6,8,8,10,5,6,7,8,9,4,10,7,4,8,10,9,6,5,6,10,6
%N Number of 5's in decimal expansion of 5^n.
%p P:=proc(n) local i,k,x,y,w,cont; y:=5; k:=y; for i from 0 by 1 to n do x:=y^i; cont:=0; while x>0 do w:=x-trunc(x/10)*10; if w=k then cont:=cont+1; fi; x:=trunc(x/10); od; print(cont); od; end: P(100);
%Y Cf. A065710, A126205, A126206, A126208, A126209, A126210, A126211.
%K nonn,base
%O 0,7
%A _Paolo P. Lava_ and _Giorgio Balzarotti_, Dec 20 2006