1,1

The logarithmic integral can be computed in PARI: Li(x) = -eint1(log(1/x)).

Next term is A089897(858), which has 256 digits.

In fact the prime terms are for n=2, 3, 5, 9, 10, 26, 57, 202, 858, 1508, 1552, 2285, 4244, (5000). - Robert G. Wilson v

Table of n, a(n) for n=1..8.

Select[ Floor[ LogIntegral[ 2^Range[202]]], PrimeQ[ # ] &] (* Robert G. Wilson v, Nov 09 2005 *)

(PARI) lip(n) = forstep(x=1, n, 1, y=floor(-eint1(log(1/2^x))); if(isprime(y), print1(y", ")))

Cf. A089897.

Sequence in context: A100843 A082101 A158712 * A120266 A230518 A241248

Adjacent sequences: A090469 A090470 A090471 * A090473 A090474 A090475

nonn

Cino Hilliard, Feb 01 2004

Edited by David Wasserman, Nov 08 2005

approved