OFFSET
1
COMMENTS
Proof for the formula a(n) = A353269(A332462(n)): This follows from a more general identity A048675(n) == A156552(A019565(A156552(n))) (mod 3). Applying A156552's inverse, the Doudna-map x -> A005940(1+x), to the both sides from the right we obtain A087808(n) == A048678(n) (mod 3), and from the respective recurrences of those two sequences it is easy to see that they are equal when reduced modulo 3.
LINKS
FORMULA
MATHEMATICA
f[p_, e_] := e*2^(PrimePi[p] - 1); a[1] = 1; a[n_] := Boole @ Divisible[Plus @@ f @@@ FactorInteger[n], 3]; Array[a, 100] (* Amiram Eldar, Apr 15 2022 *)
PROG
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Apr 15 2022
STATUS
approved