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%I #15 Jan 29 2022 00:42:31
%S 1,1,1,2,2,2,4,6,8,8,10,18,34,52,52,24,58,136,288,472,472,66,186,538,
%T 1424,3224,5504,5504,180,614,2080,6648,18888,44712,78416,78416,522,
%U 2034,7970,29700,101340,302096,738448,1320064,1320064
%N Triangle of series-parallel numbers.
%D J. Riordan, An Introduction to Combinatorial Analysis, Wiley, 1958, p. 142.
%e Triangle begins
%e 1;
%e 1, 1;
%e 2, 2, 2;
%e 4, 6, 8, 8;
%e ...
%K nonn,easy,tabl,nice
%O 0,4
%A _N. J. A. Sloane_
%E a(35) corrected by _Sean A. Irvine_, Nov 15 2020
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