A108955 Floor(Li(2n) - Li(n)).

1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 10, 10, 10, 10, 10, 10, 11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 16, 16, 16, 16, 16, 16, 17, 17, 17

Offset

2,2

Links

Table of n, a(n) for n=2..84.

Formula

Li(x) = Int(t=2, x, dt/log(t)) = Logarithmic Integral.

Mathematica

Table[Floor[LogIntegral[2n]-LogIntegral[n]], {n, 2, 90}] (* Harvey P. Dale, Jun 21 2017 *)

Prog

(PARI) L(n) = for(x=2, n, y=Li(2*x)-Li(x); print1(floor(y)", ")) Li(x) = \ Logarithmic integral { -eint1(log(1/x)) }

Crossrefs

Sequence in context: A232746 A052146 A097882 * A108956 A289133 A367194

Adjacent sequences: A108952 A108953 A108954 * A108956 A108957 A108958

Keyword

easy,nonn

Author

Cino Hilliard, Jul 22 2005

Status

approved