A091828 a(n)=n-2*valuation(A000254(n),3).

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, 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, 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

Offset: 1

Author

Benoit Cloitre, Mar 09 2004

Keywords

• nonn

Crossrefs

Cf. A056792.

Programs

PARI

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

Formula

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