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

1,2

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

Formula

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

Prog

(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

Crossrefs

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

Sequence in context: A218862 A243199 A305212 * A087263 A099894 A048298

Adjacent sequences: A104771 A104772 A104773 * A104775 A104776 A104777

Keyword

nonn

Author

Reinhard Zumkeller, Mar 24 2005

Extensions

Name changed by Antti Karttunen, Apr 01 2021

Status

approved