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

1,3

Links

Table of n, a(n) for n=1..89.

Formula

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

Prog

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

Crossrefs

Cf. A056792.

Sequence in context: A144786 A247369 A009389 * A305972 A121845 A239639

Adjacent sequences: A091825 A091826 A091827 * A091829 A091830 A091831

Keyword

nonn

Author

Benoit Cloitre, Mar 09 2004

Status

approved