|
COMMENT
|
Inspired by a formula in the reference, the study of the singular points of planar
differential systems leads to 3 two-dimensional polynomial families,
one ordinary (degenerate case, considered in one dimension, see
A129326) and two odd (the second, considered in one dimension,
see A129587). The first is in one dimension
P(2n-1,x)=(n+1+x^n)*sum_{i=0..n-1} x^i/(i+1), n>=1.
The table of coefficients of P() with 2n coefficients per row
starts: 2, 1; 3, 3/2, 1, 1/2; 4, 2, 4/3, 1, 1/2, 1/3;.. .
Rows multiplied by n!, the table becomes Q()= 2, 1; 6, 3, 2, 1; 24, 12, 8, 6, 3, 2;
120, 60, 40, 30, 24, 12, 8, 6; 720, 360, 240, 180, 144,...
The sequence gives the alternating row sums of this table Q,
positive sign for coefficients in front of even and negative
sign for coefficients in front of odd powers of x.
The row sums of Q are (n+2)*A000254(n)= 3, 12, 55, 300...
Adding the alternating and ordinary row sums yields the sequence 4, 16, 70, 384....
The sequence of sums of antidiagonals in the Q table starts
2, 6+1=7, 24+3=27, 120+12+1=134.
|
