A329717 a(n) is n (plus or minus) the number of distinct primes dividing n according to parity (even or odd).

1, 1, 2, 3, 4, 8, 6, 7, 8, 12, 10, 14, 12, 16, 17, 15, 16, 20, 18, 22, 23, 24, 22, 26, 24, 28, 26, 30, 28, 27, 30, 31, 35, 36, 37, 38, 36, 40, 41, 42, 40, 39, 42, 46, 47, 48, 46, 50, 48, 52, 53, 54, 52, 56, 57, 58, 59, 60, 58, 57, 60, 64, 65, 63, 67, 63, 66

Offset: 1

Author

Lars Blomberg, Nov 20 2019

Keywords

• nonn

Examples

			A001221(3) = 1, so a(3) = 3-1 = 2. A001221(6) = 2, so a(6) = 6+2 = 8.
		

Links

• Lars Blomberg, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001221, A229109.

Programs

Mathematica

Array[# + (om = PrimeNu[#]) * (-1)^om &, 67] (* Amiram Eldar, Nov 23 2019 *)

PARI

a(n) = my(om=omega(n)); n + (-1)^om*om; \\ Michel Marcus, Nov 20 2019

Formula

a(n) = n + A001221(n)*(-1)^A001221(n).