A174950 Size of sea of semiprimes surrounding n-th prime.

0, 1, 2, 1, 2, 2, 0, 0, 2, 0, 0, 2, 0, 0, 1, 0, 2, 1, 0, 0, 1, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 1, 0, 2, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 2, 0, 1, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 1, 0, 0, 0, 2, 0, 0, 0, 2, 0, 0, 1, 0, 0

Offset

1,3

Comments

Numbers of previous and following semiprimes of n-th prime.

Links

Table of n, a(n) for n=1..105.

Example

a(1)=0 because first prime is in a sea of 0 semiprimes; a(2)=1 because 2nd prime is in a sea of 1 semiprimes (3, 4); a(3)=2 because 3rd prime is in a sea of 2 semiprimes (4, 5, 6); a(4)=1 because 4th prime is in a sea of 1 semiprimes (6, 7); a(4)=2 because 5th prime is in a sea of 2 semiprimes (9, 10, 11).

Crossrefs

Cf. A000040, A001358, A046930, A159461.

Sequence in context: A088151 A286129 A230322 * A159906 A263444 A276321

Adjacent sequences: A174947 A174948 A174949 * A174951 A174952 A174953

Keyword

nonn

Author

Juri-Stepan Gerasimov, Apr 02 2010

Extensions

Corrected by Ray Chandler, Apr 06 2010

Status

approved