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A369026 a(n) = floor(n^(n - 1) / 2) for n > 0 and otherwise 0.

%I A369026 #11 Jan 12 2024 15:15:48
%S A369026 0,0,1,4,32,312,3888,58824,1048576,21523360,500000000,12968712300,
%T A369026 371504185344,11649042561240,396857386627072,14596463012695312,
%U A369026 576460752303423488,24330595937833434240,1092955779869348265984
%N A369026 a(n) = floor(n^(n - 1) / 2) for n > 0 and otherwise 0.
%t A369026 A369026[n_] := If[n > 0, Floor[n^(n-1) / 2], 0];
%t A369026 Array[A369026, 30, 0] (* _Paolo Xausa_, Jan 12 2024 *)
%o A369026 (SageMath)
%o A369026 def A369026(n): return n^(n - 1) // 2 if n > 0 else 0
%o A369026 print([A369026(n) for n in range(22)])
%Y A369026 Cf. A000169, A369025, A369027.
%K A369026 nonn
%O A369026 0,4
%A A369026 _Peter Luschny_, Jan 12 2024