0,2

A048998 with all rows reversed is

1

2.....-1

6.....-6...1

24...-36..12.0

120.-240.120.0.-4

The signed antidiagonal sums are sum_{m=0..n/1}(-1)^m*A048998(n-m,n-2m) = 1, 2, 7, 30, 157, 972, 6960, 56640, 516596,...

Half sums 1, 2, 6, 24, 121,... [what are "half sums? - N. J. A. Sloane (njas(AT)research.att.com), Jul 12 2008]

The antidiagonal sums of A048998 in its original order are 1, -1, 3, -6, 14, -36, 144, -240, -6576, -1800, 2143560, -15120,...

a(n) = sum_{m=0..n/2} A048998(n-m,n-2m). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 12 2008

a(3)=24-6=18. a(4)=120-36+1=85.

Sequence in context: A157312 A089412 A058798 this_sequence A020029 A020119 A109995

Adjacent sequences: A122593 A122594 A122595 this_sequence A122597 A122598 A122599

nonn,uned

Paul Curtz (bpcrtz(AT)free;fr1), Jun 07 2007

Partially edited and extended by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 12 2008