OFFSET
1,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..300
Vladimir Pletser, Congruence conditions on the number of terms in sums of consecutive squared integers equal to squared integers, arXiv:1409.7969 [math.NT], 2014.
Index entries for linear recurrences with constant coefficients, signature (1, 0, 64, -64).
FORMULA
G.f.: x*(1+2*x+4*x^2)/((-1+x)*(-1+4*x)*(1+4*x+16*x^2)). - Vaclav Kotesovec, Nov 28 2012
a(1)=1, a(2)=3, a(3)=7, a(4)=71, a(n)=a(n-1)+64*a(n-3)-64*a(n-4). - Harvey P. Dale, Nov 18 2013
MATHEMATICA
CoefficientList[Series[(1 + 2 x + 4 x^2) / ((-1 + x) (-1 + 4 x) (1 + 4 x + 16 x^2)), {x, 0, 30}], x] (* Vincenzo Librandi, May 19 2013 *)
LinearRecurrence[{1, 0, 64, -64}, {1, 3, 7, 71}, 30] (* Harvey P. Dale, Nov 18 2013 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Artur Jasinski, Jan 27 2006
EXTENSIONS
Edited with better definition and offset corrected by Omar E. Pol, Jan 08 2009
STATUS
approved