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%I #28 Jun 29 2023 11:00:40
%S 1,4,80,7104,3292184,6523266332,56203566442908,2176852129116199068,
%T 373334515946952014204102,281931891850296665963970600460,
%U 939652851372937937187518231503848142,13807942929878598929190143960742601141566220,893498265685263112931409501489577970162598024007690
%N Number of Hamiltonian circuits within parallelograms of size n X n on the triangular lattice.
%H Ed Wynn, <a href="/A339854/b339854.txt">Table of n, a(n) for n = 2..16</a>
%e a(2) = 1:
%e *---*
%e / /
%e *---*
%e a(3) = 4:
%e * *---* *---*---*
%e / \ / / \ /
%e * * * *---* *
%e / / / /
%e *---*---* *---*---*
%e *---*---* *---*---*
%e / / / /
%e * * * * *---*
%e / / \ / / \
%e *---* * *---*---*
%Y Main diagonal of A339849.
%Y Cf. A140519.
%K nonn
%O 2,2
%A _Seiichi Manyama_, Dec 19 2020
%E More terms from _Ed Wynn_, Jun 28 2023