OFFSET
0,4
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..16384
FORMULA
G.f.: x * Product_{k>=0} (1 + x^(2^k) + 4*x^(2^(k+1))).
a(n) == 1 (mod 4) for n >= 1. - Hugo Pfoertner, Mar 17 2021
MAPLE
a:= proc(n) option remember; `if`(n<2, n, (q->
`if`(d=1, 4*a(q)+a(q+1), a(q)))(iquo(n, 2, 'd')))
end:
seq(a(n), n=0..68); # Alois P. Heinz, Mar 17 2021
MATHEMATICA
a[0] = 0; a[1] = 1; a[n_] := If[EvenQ[n], a[n/2], 4 a[(n - 1)/2] + a[(n + 1)/2]]; Table[a[n], {n, 0, 68}]
nmax = 68; CoefficientList[Series[x Product[(1 + x^(2^k) + 4 x^(2^(k + 1))), {k, 0, Floor[Log[2, nmax]] + 1}], {x, 0, nmax}], x]
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Mar 17 2021
STATUS
approved