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%I #7 Jul 30 2017 23:02:30
%S 1,1,2,2,1,4,6,5,7,8,7,8,10,11,12,13,14,12,14,12,18,19,20,22,20,22,23,
%T 24,25,26,30,27,28,29,31,32,33,34,35,36,35,36,38,39,40,41,42,38,39,43,
%U 45,46,47,49,53,54,55,55,57,55,52,53,56,61,62,60,62,62,63,64,68,64,65
%N Distance to the largest Catalan number which is less than, but divides the n-th Catalan number; i.e., a(n) gives minimum k (> 0) such that C_{n-k}|C_n.
%e a(5) = 1 because C_4 (= 14) divides C_5 (= 42).
%p [seq(WCD(j),j=1..100)]; WCD := proc(n) local i; for i from n-1 by -1 to 0 do if(0 = (`mod`(Cat(n),Cat(i)))) then RETURN(n-i); fi; od; end; Cat := n -> (binomial(2*n,n)/(n+1));
%t a[n_] := For[k = n - 1, True, k--, If[Divisible[CatalanNumber[n], CatalanNumber[k]], Return[n - k]]]; a[1] = 1; Array[a, 100] (* _Jean-François Alcover_, Mar 06 2016 *)
%Y Cf. A000108.
%K nonn
%O 1,3
%A _Antti Karttunen_, Jun 13 2001
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