A236627 Number of positive integers <= sqrt(n) not dividing n.

0, 0, 0, 0, 1, 0, 1, 0, 1, 1, 2, 0, 2, 1, 1, 1, 3, 1, 3, 1, 2, 2, 3, 0, 3, 3, 3, 2, 4, 1, 4, 2, 3, 3, 3, 1, 5, 4, 4, 2, 5, 2, 5, 3, 3, 4, 5, 1, 5, 4, 5, 4, 6, 3, 5, 3, 5, 5, 6, 1, 6, 5, 4, 4, 6, 4, 7, 5, 6, 4, 7, 2, 7, 6, 5, 5, 6, 4, 7, 3, 6, 7, 8, 3, 7, 7, 7, 5, 8, 3, 7, 6, 7, 7, 7, 3, 8, 6, 6, 5, 9

Offset: 1

Author

Omar E. Pol, Feb 05 2014

Keywords

• nonn

Comments

It appears that the indices of the zeros in the sequence are in A018253.

Links

• Omar E. Pol, , Three illustrations of A000005 giving the structure of this sequence, (2013)

Crossrefs

Cf. A000005, A000196, A010052, A018253, A038548, A007491, A160812, A161205, A212119, A228813, A228814, A229940, A229942, A229944, A229950, A229951.

Programs

PARI

a(n) = sum(i=1, sqrtint(n), (n % i) != 0); \\ Michel Marcus, Mar 16 2014

Formula

a(n) = A000196(n) - A038548(n) = A160812(n)/2.