2692030

Appears in sequences

• Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and two, three or four distinct values.at n=4A211820
• a(n) = (2*n + 1)*(12 + 11*n + 93*n^2 + 4*n^3)/3.at n=27A387439