A091828 - OEIS

%I #5 Mar 30 2012 18:39:22

%S 1,0,3,4,5,2,1,4,5,6,7,6,7,8,7,8,9,4,5,6,3,2,5,6,7,8,7,8,9,8,9,10,9,

%T 10,11,8,9,10,9,10,11,10,11,12,9,10,11,10,11,12,11,12,13,6,7,8,7,8,9,

%U 8,9,10,5,6,7,4,5,6,7,8,9,8,9,10,9,10,11,10,11,12,9,10,11,10,11,12,11,12,13

%N a(n)=n-2*valuation(A000254(n),3).

%F For n>7 a(3n)=a(n)+2; a(3n+1)=a(n)+3; (3n+2)=a(n)+4

%o (PARI) a(n)=if(n<2,1,n-2*valuation(n!*sum(i=1,n,1/i),3))

%Y Cf. A056792.

%K nonn

%O 1,3

%A _Benoit Cloitre_, Mar 09 2004