A213642 a(n) = prime(odd part of n).

2, 2, 5, 2, 11, 5, 17, 2, 23, 11, 31, 5, 41, 17, 47, 2, 59, 23, 67, 11, 73, 31, 83, 5, 97, 41, 103, 17, 109, 47, 127, 2, 137, 59, 149, 23, 157, 67, 167, 11, 179, 73, 191, 31, 197, 83, 211, 5, 227, 97, 233, 41, 241, 103, 257, 17, 269, 109, 277, 47, 283, 127

Offset

1,1

Comments

If you take every second term of a(n) you get A031368.

Links

Table of n, a(n) for n=1..62.

Formula

a(n) = A000040(A000265(n)).

Example

a(8) = prime(odd part of 8) = prime(1) = 2.
a(9) = prime(odd part of 9) = prime(9) = 23.
a(10) = prime(odd part of 10) = prime(5) = 11.

Mathematica

Table[Prime[n/2^IntegerExponent[n, 2]], {n, 100}] (* T. D. Noe, Jun 18 2012 *)

Prog

(Python)
from sympy import sieve
def a(n):
    while not n&1: n >>= 1
    return sieve[n]
print([a(n) for n in range(1, 63)]) # Michael S. Branicky, Jun 26 2025

Crossrefs

Cf. A031368, A000265, A000040.

Sequence in context: A083456 A211932 A389785 * A344753 A353860 A303073

Adjacent sequences: A213639 A213640 A213641 * A213643 A213644 A213645

Keyword

nonn

Author

Jens Ahlström, Jun 17 2012

Extensions

Name clarified by Michael S. Branicky, Jun 26 2025

Status

approved