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A174950 Size of sea of semiprimes surrounding n-th prime. 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 17 00:35 EDT 2021. Contains 348048 sequences. (Running on oeis4.)