OFFSET
0,3
LINKS
Jinyuan Wang, Table of n, a(n) for n = 0..1000
MATHEMATICA
r[n_]:=Reduce[{x, y}.{{2, 1}, {1, 5}}.{x, y}==n, {x, y}, Integers]; Table[rn=r[n]; Which[rn===False, 0, Head[rn]===Or, Length[rn], Head[rn]===And, 1], {n, 0, 105}] (* Vincenzo Librandi, Feb 22 2020 *)
PROG
(PARI) a(n) = if(n<1, n==0, qfrep([2, 1; 1, 5], n)[n]*2); \\ Jinyuan Wang, Feb 21 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
More terms from Jinyuan Wang, Feb 21 2020
STATUS
approved