OFFSET
1,1
COMMENTS
When are both n-1 and 17*n-1 perfect squares? This problem gives the equation 17*x^2+16=y^2.
LINKS
Index entries for linear recurrences with constant coefficients, signature (0,0,66,0,0,-1).
FORMULA
a(n) = 66*a(n-3) - a(n-6), a(1)=4, a(2)=13, a(3)=21, a(4)=132, a(5)=837, a(6)=1373.
G.f.: -x*(13*x^5+21*x^4+132*x^3-21*x^2-13*x-4) / (x^6-66*x^3+1). - Colin Barker, Sep 01 2013
EXAMPLE
a(7)=66*132-4=8708.
MATHEMATICA
LinearRecurrence[{0, 0, 66, 0, 0, -1}, {4, 13, 21, 132, 837, 1373}, 50]
PROG
(PARI) Vec(-x*(13*x^5+21*x^4+132*x^3-21*x^2-13*x-4)/(x^6-66*x^3+1) + O(x^100)) \\ Colin Barker, Sep 01 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Sture Sjöstedt, Nov 10 2011
EXTENSIONS
More terms from T. D. Noe, Nov 10 2011
STATUS
approved