OFFSET
1,1
COMMENTS
Prime numbers q for which the number of prime numbers smaller than q is also a prime number.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..10000
EXAMPLE
a(4)=prime(prime(4)+1), prime(4)=7, hence a(4)=prime(8)=19.
163 is in the sequence because (1) it is a prime number, (2) there are 37 prime numbers smaller than 163 and 37 is also a prime number.
MAPLE
with(numtheory): seq(ithprime(ithprime(i)+1), i=1..51);
MATHEMATICA
Prime[Prime[Range[60]]+1] (* Harvey P. Dale, Nov 07 2016 *)
PROG
(PARI) a(n) = prime(prime(n)+1); \\ Michel Marcus, Nov 17 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Mark Hudson (mrmarkhudson(AT)hotmail.com), Jul 05 2002
EXTENSIONS
Edited by N. J. A. Sloane, Nov 04 2018 at the suggestion of Georg Fischer, Nov 03 2018, merging a duplicate entry with this one.
STATUS
approved