A195416 Primes p such that there is only one semiprime number between prime(p) and prime(p+1).

2, 3, 19, 29, 31, 59, 73, 149, 179, 199, 211, 271, 281, 311, 337, 347, 349, 359, 433, 449, 479, 523, 547, 659, 661, 683, 727, 733, 809, 821, 823, 829, 857, 877, 947, 977, 983, 1049, 1129, 1181, 1201, 1213, 1291, 1297, 1301, 1307, 1321, 1367, 1429, 1433, 1439, 1451, 1489, 1493, 1511, 1553, 1567

Offset

1,1

Links

Table of n, a(n) for n=1..57.

Example

a(1)=2 because 2 is a prime and prime(2)=3<(only one semiprime 4)<5=prime(2+1), a(2)=3 because 3 is a prime and prime(3)=5<(only one semiprime 6)<7=prime(3+1), a(3)=19 because 19 is a prime and prime(19)=67<(only one semiprime 69)<71=prime(19+1).

Crossrefs

Cf. A103668, A001358, A006450, A195190.

Sequence in context: A215361 A090476 A127941 * A215383 A215387 A140555

Adjacent sequences: A195413 A195414 A195415 * A195417 A195418 A195419

Keyword

nonn

Author

Juri-Stepan Gerasimov, Sep 17 2011

Extensions

Corrected by R. J. Mathar, Sep 20 2011

Status

approved