

A072677


a(n) = prime(prime(n)+1) where prime(k) is the kth prime.


13



5, 7, 13, 19, 37, 43, 61, 71, 89, 113, 131, 163, 181, 193, 223, 251, 281, 293, 337, 359, 373, 409, 433, 463, 521, 557, 569, 593, 601, 619, 719, 743, 787, 809, 863, 881, 929, 971, 997, 1033, 1069, 1091, 1163, 1181, 1213, 1223, 1301, 1423, 1439, 1451, 1481, 1511, 1531, 1601, 1627, 1693, 1733, 1747, 1789, 1831, 1861, 1931
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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

Cf. A000720, A006450, A055003, A072677.
Sequence in context: A264865 A293712 A297674 * A117249 A063910 A288632
Adjacent sequences: A072674 A072675 A072676 * A072678 A072679 A072680


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



