OFFSET
1,3
COMMENTS
Each n occurs at two positions, the distances between them are: 1, 1, 1, 1, 2, 3, 5, 5, 8, 13, 13, 17, 20, 21, 23, 28, 33, 34, 39, 41, 41, ... - Zak Seidov, Mar 06 2011
LINKS
Reinhard Zumkeller, Table of n, a(n) for n = 1..10000
FORMULA
MATHEMATICA
m=100; pr=Prime[Range[m]]; npr=Select[Range[m], !PrimeQ[#]&];
a[n_]:=If[PrimeQ[n], PrimePi[n], Position[npr, n][[1, 1]]]; Table[a[n], {n, m}] (* Zak Seidov Mar 05 2011 *) s=Range[500]; Do[s=Insert[s, n, Prime[n]], {n, 100}]; s (* Zak Seidov, Mar 05 2011 *)
PROG
(Haskell)
a026233 n = a049084 n + a239968 n
-- Reinhard Zumkeller, Mar 30 2014, Feb 12 2014
(PARI) first(n)=my(p, c); vector(n, k, if(isprime(k), p++, c++)) \\ Charles R Greathouse IV, Sep 02 2015
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved