OFFSET
0,2
COMMENTS
A diagonal of the square array A223968.
LINKS
Index entries for linear recurrences with constant coefficients, signature (9,-28,35,-15,1).
FORMULA
a(n) = A223968(n+2,n).
G.f.: (1-x)^2*(1-3*x)/(1-9*x+28*x^2-35*x^3+15*x^4-x^5).
a(n) = 9*a(n-1) - 28*a(n-2) + 35*a(n-3) - 15*a(n-4) + a(n-5) with a(0) = 1, a(1) = 4, a(2) = 15, a(3) = 55, a(4) = 200.
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Philippe Deléham, Apr 07 2013
STATUS
approved