OFFSET

0,1

COMMENTS

LINKS

S. Segal, On pi(x+y)<=pi(x)+pi(y), Transactions American Mathematical Society, 104 (1962), 523-527.

EXAMPLE

n=24, the relevant list is: {16777216,1077871,84115,8198,1028,172,39,12,5,3,2,1,0}, its length a(24)=13.

MATHEMATICA

Table[Length[FixedPointList[PrimePi, 2^w]]-1, {w, 0, 32}]

f[n_] := Length@ NestWhileList[ PrimePi, 2^n, # > 0 &]; Array[f, 48, 0] (* Robert G. Wilson v, Aug 12 2011 *)

PROG

(PARI) a(n) = {my(c=2, k=2^n); while(k=primepi(k), c++); c; } \\ Jinyuan Wang, May 16 2020

CROSSREFS

KEYWORD

nonn

AUTHOR

Labos Elemer, Mar 19 2001

EXTENSIONS

More terms from David Wasserman, May 31 2002

STATUS

approved