A104774 a(1) = 1, a(2) = 2, a(3) = 0, a(4) = 4, and for n > 4, if n is an even number, a(n) = a(n/2) - (1 if a(n/2) is not zero), otherwise if n is an odd semiprime p*q (with q >= p), then a(n) = p+q, otherwise 0.

1, 2, 0, 4, 0, 0, 0, 3, 6, 0, 0, 0, 0, 0, 8, 2, 0, 5, 0, 0, 10, 0, 0, 0, 10, 0, 0, 0, 0, 7, 0, 1, 14, 0, 12, 4, 0, 0, 16, 0, 0, 9, 0, 0, 0, 0, 0, 0, 14, 9, 20, 0, 0, 0, 16, 0, 22, 0, 0, 6, 0, 0, 0, 0, 18, 13, 0, 0, 26, 11, 0, 3, 0, 0, 0, 0, 18, 15, 0, 0, 0, 0, 0, 8, 22, 0, 32, 0, 0, 0, 20, 0, 34, 0, 24

Offset: 1

Author

Reinhard Zumkeller, Mar 24 2005

Keywords

• nonn

Comments

The original name was: If n is even then (if n<=4 then n else a(n/2) + 0^a(n/2) - 1) else (if n=p*q is semiprime then p+q else 0^(n-1))).

Links

• Antti Karttunen, Table of n, a(n) for n = 1..16384
• Antti Karttunen, Data supplement: n, a(n) computed for n = 1..65537

Crossrefs

Cf. A001358, A046315, A090967, A104772, A104773.

Programs

PARI

A104774(n) = if(!(n%2),if(n<=4,n,my(u=A104774(n/2)); (u+!u-1)),if(2==bigomega(n),my(f=factor(n)[,1]); if(1==omega(n),2*f[1],f[1]+f[2]), !(n-1))); \\ Antti Karttunen, Mar 30 2021

Formula

a(A104772(n)) = n; a(A104773(n)) = A104772(n).

Extensions

Name changed by Antti Karttunen, Apr 01 2021