A335420 a(n) = A000120(A163511(n)).

1, 1, 1, 2, 1, 2, 2, 2, 1, 4, 2, 3, 2, 4, 2, 3, 1, 3, 4, 6, 2, 4, 3, 3, 2, 4, 4, 3, 2, 3, 3, 3, 1, 6, 3, 5, 4, 7, 6, 6, 2, 4, 4, 6, 3, 4, 3, 5, 2, 4, 4, 6, 4, 4, 3, 4, 2, 6, 3, 5, 3, 2, 3, 3, 1, 6, 6, 6, 3, 7, 5, 5, 4, 5, 7, 7, 6, 3, 6, 6, 2, 5, 4, 5, 4, 8, 6, 7, 3, 6, 4, 6, 3, 6, 5, 4, 2, 5, 4, 7, 4, 4, 6, 5, 4, 6

Offset: 0

Author

Antti Karttunen, Jun 09 2020

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 0..65537
• Index entries for sequences related to binary expansion of n

Crossrefs

Cf. A000079 (positions of ones), A000120, A001222, A163511, A335421, A335422.

Cf. also A323901, A334204.

Programs

PARI

A005940(n) = { my(p=2, t=1); n--; until(!n\=2, if((n%2), (t*=p), p=nextprime(p+1))); t };
A054429(n) = ((3<<#binary(n\2))-n-1);
A163511(n) = if(!n,1,A005940(1+A054429(n)));
A335420(n) = hammingweight(A163511(n));

Python

from sympy import nextprime
def A335420(n):
    c, p, k = 1, 1, n
    while k:
        c *= (p:=nextprime(p))**(s:=(~k&k-1).bit_length())
        k >>= s+1
    return (c*p).bit_count() # Chai Wah Wu, Jul 25 2023

Formula

a(n) = A000120(A163511(n)).

a(n) = A001222(A335422(n)).

a(n) = a(2n) = a(A000265(n)).

For all n >= 0, a(2^n) = 1.