1,6

a(n)>=1 because there is always at least one square between p and 2p.

Table of n, a(n) for n=1..103.

a(n) = A000196(2*prime(n)) - A000196(prime(n)-1).

a(6)=2 because between 13 and 2*13 there are two squares: 4^2 and 5^2.

f[n_] := Floor[Sqrt[n]]; Table[f[2Prime[n]] - f[Prime[n] - 1], {n, 100}]

Cf. A000196, A105224.

Sequence in context: A024937 A143977 A115265 * A025859 A031281 A203181

Adjacent sequences: A105220 A105221 A105222 * A105224 A105225 A105226

easy,nonn

Giovanni Teofilatto, Apr 14 2005

Edited and extended by Ray Chandler, Apr 16 2005

approved