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

Author

Antti Karttunen, Jul 17 2020

Keywords

• nonn

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

Crossrefs

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

Cf. A336119 (positions of zeros).

Programs

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)));

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).