|
%I #6 Mar 30 2012 18:50:49
%S 1,2,8,4,18,9,30,15,42,21,70,35,66,33,78,39,130,65,102,51,114,57,190,
%T 95,138,69,230,115,322,161,174,87,186,93,310,155,434,217,222,111,370,
%U 185,246,123,258,129,430,215,282,141,470,235,658,329,318,159,530,265,742
%N If n<=2 then n else (if n is odd then 2*a(n+1) else p*q, where n=p+q, p<=q, primes).
%C Encoding of positive integers based on the Goldbach conjecture, see A104774 for decoding: A104774(A104772(n))=n;
%C a(n - n mod 2) = (2^(1 + n mod 2)) * A020481(floor(n/2))*A020482(floor(n/2));
%C for numbers greater than 4: a(even) = odd and a(odd) = even;
%C A001222(a(n)) = A010693(n) for n>2;
%C a(a(n)) = A104773(n).
%H <a href="/index/Go#Goldbach">Index entries for sequences related to Goldbach conjecture</a>
%F For k>1: a(2*k)=A020481(k)*A020482(k) and a(2*k-1)=2*a(2*k).
%Y Cf. A001358, A046315, A090967.
%K nonn
%O 1,2
%A _Reinhard Zumkeller_, Mar 24 2005
|
