A336121 a(1) = 0, and for n > 1, a(n) = [A122111(n) == 3 (mod 4)] + a(A253553(n)).

0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 2, 0, 2, 0, 1, 0, 1, 0, 2, 1, 1, 0, 1, 0, 2, 0, 3, 0, 1, 1, 1, 0, 1, 0, 2, 0, 2, 0, 1, 0, 1, 0, 3, 0, 1, 0, 1, 0, 3, 1, 2, 0, 1, 0, 1, 0, 1, 0, 3, 1, 2, 0, 1, 0, 1, 0, 2, 0, 1, 1, 1, 0, 2, 0, 3, 0, 1, 0, 1, 1, 1, 0, 2, 0, 3, 0, 1, 0, 1, 1, 3, 0, 2, 0, 2, 0, 2, 0, 2, 1

Offset

1,16

Comments

Positions for the first occurrence of each n, for n >= 0, are: 1, 4, 16, 32, 144, 512, 2048, 6912, 20736, 62208, ...

Links

Antti Karttunen, Table of n, a(n) for n = 1..65537

Formula

a(1) = 0, and for n > 1, a(n) = [A336124(n) == 3] + a(A253553(n)).

a(n) = A000120(A336120(n)).

a(n) = A292377(A122111(n)).

a(n) = A001222(n) - A336123(n).

Prog

(PARI)
A253553(n) = if(n<=2, 1, my(f=factor(n), k=#f~); if(f[k, 2]>1, f[k, 2]--, f[k, 1] = precprime(f[k, 1]-1)); factorback(f));
A336121(n) = if(1==n, 0, (3==A336124(n))+A336121(A253553(n)));

Crossrefs

Cf. A000120, A001222, A122111, A253553, A292377, A292383, A336120, A336123, A336124.

Cf. A336119 (positions of zeros).

Sequence in context: A004556 A263635 A358233 * A363795 A214332 A164734

Adjacent sequences: A336118 A336119 A336120 * A336122 A336123 A336124

Keyword

nonn

Author

Antti Karttunen, Jul 17 2020

Status

approved