a binomial sum.

[pin]

Hello seqfans!

I was about to submit the following signed sequence (offset 0),

1, -1, 7, -21, 81, -295, 1107, -4165, 15793, -60171, 230253, -884235, 3406105, -13154947, 50922987, -197519941, 767502945, -2987013067, 11641557717, -45429853651, 177490745985, ...,

but thought that I post here first requesting if someone is able to find a closed form of it.  Here is the sum that generates the sequence in Maple code.

a:=n->sum(sum(binomial(j-n-1,m),m=0..n),j=0..n);

Any ideas?

-Francois.

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