A121896 - OEIS

%I #12 May 06 2021 16:30:03

%S 1,4,8,14,20,30,37,51,61,76,89,111,120,146,165,187,205,239,255,293,

%T 312,344,375,421,434,479,516,558,587,645,664,726,760,812,861,919,937,

%U 1011,1066,1128,1159,1241,1272,1358,1407,1465,1532,1626,1647,1738,1796,1878

%N Let M be the matrix defined in A111490. Sequence gives M(1,1), M(1,2)+M(1,2)+M(2,2), M(1,3)+M(2,3)+M(3,1)+M(3,2)+M(3,3), etc.

%F a(n) = -M(n,n) + Sum_{i=1..n} (M(i,n) + M(n,i)).

%e a(4) = 1+2+1+1+2+3+4 = 14.

%Y Cf. A111490.

%K easy,nonn

%O 1,2

%A _Paolo P. Lava_ and _Giorgio Balzarotti_, Sep 01 2006