150057

Appears in sequences

• Number of (n+1) X (n+1) -4..4 symmetric matrices with every 2 X 2 subblock having sum zero and one or two distinct values.at n=21A211490
• Expansion of (1/x) * Series_Reversion( x * (1-x)^2 * (1-x+x^2) ).at n=7A368938