OFFSET
1,1
COMMENTS
Values of c are in A117475
LINKS
Index entries for linear recurrences with constant coefficients, signature (1,6,-6,-1,1).
FORMULA
a(1)=12, a(2)=33, a(3)=133, a(4)=252, a(n) = 6*a(n-2) - a(n-4) + 46.
G.f.: x*(8*x^4+7*x^3-28*x^2-21*x-12) / ((x-1)*(x^2-2*x-1)*(x^2+2*x-1)). [Colin Barker, Dec 17 2012]
EXAMPLE
a(5) = 6*133 - 12 + 46 = 832 and 832^2 + 855^2 = 1193^2 and 855-832=23 and gcd(832,855,1193)=1
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Andras Erszegi (erszegi.andras(AT)chello.hu), Mar 19 2006
STATUS
approved