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%I
%S 3,5,14,42,132,429,1430,4862,16796,58786,208012,742900,2674440,
%T 9694845,35357670,129644790,477638700,1767263190,6564120420,
%U 24466267020,91482563640,343059613650,1289904147324,4861946401452,18367353072152,69533550916004,263747951750360
%N First terms of first rows of zigzag matrices as defined in A088961.
%C a(n) = A088961(A056520(n-1));
%C a(n) = A000108(n+1) for n > 1.
%H Reinhard Zumkeller, <a href="/A230585/b230585.txt">Table of n, a(n) for n = 1..1000</a>
%F a(n) = binomial(2*n,n) - binomial(2*n,n+2) + 0^(n-1).
%o (Haskell)
%o a230585 1 = 3
%o a230585 n = a007318 (2*n) n - a007318 (2*n) (n+2)
%Y Cf. A007318.
%K nonn
%O 1,1
%A _Reinhard Zumkeller_, Oct 25 2013
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