OFFSET
0,19
COMMENTS
This sequence is a signed variant of A309262.
LINKS
Rémy Sigrist, Table of n, a(n) for n = 0..10000
EXAMPLE
a(9) = a(floor(9/2^2)) - a(floor(9/3^3)) = a(2) - a(1) = 0 - 1 = -1.
MATHEMATICA
Join[{0}, Clear[a]; a[0]=0; a[1]=1; a[n_]:=a[n]=Sum[a[Floor[n/k^2]](-1)^k, {k, 2, n}]; Table[a[n], {n, 1, 100}]] (* Vincenzo Librandi, Jul 22 2019 *)
PROG
(PARI) a(n) = if (n<=1, n, sum (k=2, sqrtint(n), (-1)^k * a(n\k^2)))
CROSSREFS
KEYWORD
sign
AUTHOR
Rémy Sigrist, Jul 21 2019
STATUS
approved