43345282

Appears in sequences

• Number of (n+1)X(n+1) -9..9 symmetric matrices with every 2X2 subblock having sum zero and three distinct values.at n=20A211550
• G.f. A(x) satisfies 3*x = Sum_{n=-oo..+oo} (-1)^n * x^(3*n) * (A(x) + x^n)^(3*n) with A(0) = 1.at n=13A380682