0,2

Diagonal sums of number triangle A117377.

a(n)=sum{k=0..floor(n/2), (-1)^n*(C(k,n-2k)+4*C(k, n-2k-1))}

Sequence in context: A099310 A021880 A075013 this_sequence A007309 A084890 A058662

Adjacent sequences: A117376 A117377 A117378 this_sequence A117380 A117381 A117382

easy,sign

Paul Barry (pbarry(AT)wit.ie), Mar 10 2006