OFFSET
0,2
COMMENTS
Row sums of number triangle A119302.
LINKS
FORMULA
a(n) = a(n-1) - 2a(n-2) + a(n-3);
a(n) = Sum_{k=0..n} (C(2k, n-k) + 3*C(2k, n-k-1))*(-1)^(n-k).
MATHEMATICA
RecurrenceTable[{a[0]==1, a[1]== -2, a[2]== -4, a[n]== a[n-1] - 2*a[n-2] + a[n-3]}, a, {n, 30}] (* G. C. Greubel, Aug 07 2015 *)
LinearRecurrence[{1, -2, 1}, {1, -2, -4}, 50] (* Harvey P. Dale, Oct 11 2019 *)
CROSSREFS
KEYWORD
easy,sign
AUTHOR
Paul Barry, May 13 2006
STATUS
approved