OFFSET
1,1
COMMENTS
Also positive integers y in the solutions to 8*x^2-4*y^2+24*x+2*y+28 = 0, the corresponding values of x being A201633.
LINKS
Colin Barker, Table of n, a(n) for n = 1..1000
Index entries for linear recurrences with constant coefficients, signature (1,34,-34,-1,1).
FORMULA
a(n) = a(n-1)+34*a(n-2)-34*a(n-3)-a(n-4)+a(n-5).
G.f.: -2*x*(x^4-26*x^2+12*x+9) / ((x-1)*(x^2-6*x+1)*(x^2+6*x+1)).
EXAMPLE
18 is in the sequence because H(18) = 630 = 121+144+169+196 = 11^2+12^2+13^2+14^2.
PROG
(PARI) Vec(-2*x*(x^4-26*x^2+12*x+9)/((x-1)*(x^2-6*x+1)*(x^2+6*x+1)) + O(x^100))
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Colin Barker, Dec 21 2014
STATUS
approved