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%I #10 Feb 03 2020 03:43:05
%S 1,4,24,186,1770,19980,260820,3863160,63980280,1171195200,23476068000,
%T 511296786000,12021166357200,303414507396000,8182057223340000,
%U 234753130435824000,7139815170664176000,229442416696164672000,7767967204994540544000,276345182709766890720000
%N Let [n] = {0,...,n-1}; a(n) is number of functions f:[n] -> [n] for which there exists an injection g:[n] -> [n+1] such that for j with 0 <= j < n, either g(j) = f(j) or g(j) = f(j)+1.
%H Ariel Halpert, Flórián Lengyel and János Pach, <a href="https://doi.org/10.1016/S0166-218X(99)00240-1">Cellular telephone networks and random maps in hypergraphs</a>, Discrete Appl. Math. 103 (2000), no. 1-3, 111-126.
%F a(n) = T(n, n) where T(1, n) = n, T(2, n) = n^2, and T(m, n) = T(m, n-1) + 2*m*T(m-1, n-1) - m*T(m-1, n-2) - binomial(m, 2)*T(m-2, n-2) for 1 <= m <= n+1. - _Sean A. Irvine_, Feb 03 2020
%K nonn
%O 0,2
%A Florian Lengyel (flengyel(AT)email.gc.cuny.edu)
%E More terms from _Sean A. Irvine_, Feb 03 2020
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