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%I #6 Jul 03 2023 10:06:16
%S 1,4,16,85,481,3352,25420,223393,2157565,23241244,272933680,
%T 3496821133,48307202761,717473918560,11381186498836,192155770419673,
%U 3438337498017781,65004294514876996,1294456866053992600,27081588485949257605
%N Row sums of triangle A144881 (S1hat(3)) and of array A144880 (M31hat(3)).
%F a(n) = Sum_{m=1..n} A144881(n,m), n>=1.
%Y Cf. A144880, A144881.
%K nonn,easy
%O 1,2
%A _Wolfdieter Lang_, Oct 09 2008