OFFSET
1,1
COMMENTS
Numbers n such that the square root of 72*(n-8)*(n+9) is an integer. - Harvey P. Dale, Jun 23 2013
LINKS
Index entries for linear recurrences with constant coefficients, signature (1, 0, 6, -6, 0, -1, 1).
FORMULA
a(n) = a(n-1) + 6*a(n-3) - 6*a(n-4) - a(n-6) + a(n-7), with a(1)=8, a(2)=9, a(3)=16, a(4)=25, a(5)=40, a(6)=89, a(7)=144
G.f.: (-9*x^6 - 7*x^5 - 9*x^4 + 39*x^3 - 7*x^2 - x - 8)/(x^7 - x^6 - 6*x^4 + 6*x^3 + x - 1).
EXAMPLE
For n=2 the triangle has sides 17,9,10 with area 36.
MAPLE
MATHEMATICA
LinearRecurrence[{1, 0, 6, -6, 0, -1, 1}, {8, 9, 16, 25, 40, 89, 144}, 40] (* Harvey P. Dale, Jun 23 2013 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
James R. Buddenhagen, Oct 20 2008
STATUS
approved