A163178 a(n) is the central prime factor of A046339(n).

2, 2, 3, 2, 3, 2, 3, 2, 3, 2, 3, 2, 5, 2, 3, 3, 2, 5, 2, 5, 2, 3, 2, 2, 7, 3, 3, 5, 3, 5, 2, 3, 2, 3, 2, 2, 5, 2, 5, 3, 7, 2, 3, 7, 3, 2, 5, 2, 5, 3, 2, 3, 5, 2, 3, 7, 3, 2, 5, 2, 5, 2, 3, 2, 2, 3, 5, 7, 2, 7, 11, 3, 2, 7, 3, 3, 5, 3, 3, 2, 7, 2, 3, 2, 7, 5, 3, 2, 3, 2, 5, 11, 2, 5, 2, 3, 2, 5, 2, 2, 3, 2, 7, 5

Offset: 1

Author

Juri-Stepan Gerasimov, Jul 22 2009

Keywords

• nonn

Examples

			a(8)=2 since A046339(8) = 32 = 2*2*2*2*2.
a(9)=3 since A046339(9) = 42 = 2*3*7.
a(10)=2 since A046339(10) = 44 = 2*2*11.
a(11)=3 since A046339(11) = 45 = 3*3*5.
a(12)=2 since A046339(12) = 48 = 2*2*2*2*3.
		

Crossrefs

Cf. A046339, A162361.

Programs

Maple

cpr := proc(n) nred := n ; while numtheory[bigomega](nred) > 1 do pf := sort(convert(numtheory[factorset](nred), list)) ; nred := nred/op(1, pf)/op(-1, pf) ; od: nred ; end:
A046339 := proc(n) option remember ; if n = 1 then 8 ; else for a from procname(n-1)+1 do if not isprime(a) and numtheory[bigomega](a) mod 2 = 1 then RETURN(a) ; fi; od: fi; end:
A163178 := proc(n) cpr(A046339(n)) ; end; seq(A163178(n), n=1..120) ; # R. J. Mathar, Jul 25 2009

Extensions

More terms from R. J. Mathar, Jul 25 2009