OFFSET
0,2
COMMENTS
-24*a(n)^2 + b(n)^2 = 25, with the companion sequence b(n)= A077411(n).
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,10,0,-1).
FORMULA
EXAMPLE
24*a(2)^2 + 25 = 24*12^2 + 25 = 3481 = 59^2 = A077411(2)^2.
MATHEMATICA
CoefficientList[Series[(1+x)*(1+x+x^2)/(1-10*x^2+x^4), {x, 0, 50}], x] (* or *) LinearRecurrence[{0, 10, 0, -1}, {1, 2, 12, 21}, 30] (* G. C. Greubel, Jan 18 2018 *)
PROG
(PARI) x='x+O('x^30); Vec((1+x)*(1+x+x^2)/(1-10*x^2+x^4)) \\ G. C. Greubel, Jan 18 2018
(Magma) I:=[1, 2, 12, 21]; [n le 4 select I[n] else 10*Self(n-2) - Self(n-4): n in [1..30]]; // G. C. Greubel, Jan 18 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Nov 08 2002
STATUS
approved