

A046930


Size of sea of composite numbers surrounding nth prime.


5



1, 1, 2, 4, 4, 4, 4, 4, 8, 6, 6, 8, 4, 4, 8, 10, 6, 6, 8, 4, 6, 8, 8, 12, 10, 4, 4, 4, 4, 16, 16, 8, 6, 10, 10, 6, 10, 8, 8, 10, 6, 10, 10, 4, 4, 12, 22, 14, 4, 4, 8, 6, 10, 14, 10, 10, 6, 6, 8, 4, 10, 22, 16, 4, 4, 16, 18, 14, 10, 4, 8, 12, 12, 10, 8, 8, 12, 10, 10, 16, 10, 10, 10, 6, 8, 8
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OFFSET

1,3


LINKS

T. D. Noe, Table of n, a(n) for n=1..10000


FORMULA

a(n) = A031131(n)  2 for n > 1.  Reinhard Zumkeller, Dec 19 2013


EXAMPLE

23 is in a sea of 8 composites: 20,21,22,23,24,25,26,27,28.


MAPLE

[ seq(ithprime(i)ithprime(i2)2, i=3..100) ];


MATHEMATICA

Table[ Prime[n + 2]  Prime[n]  2, {n, 75}] (* Robert G. Wilson v Oct 27 2004 *)
Join[{1}, #[[3]]#[[1]]2&/@Partition[Prime[Range[90]], 3, 1]] (* Harvey P. Dale, Sep 26 2012 *)


PROG

(Haskell)
a046930 1 = 1
a046930 n = subtract 2 $ a031131 n  Reinhard Zumkeller, Dec 19 2013


CROSSREFS

Related sequences: A023186A023188, A046929A046931, A051650, A051652, A051697A051702, A051728A051730.
Sequence in context: A287393 A260085 A159461 * A302254 A160409 A035645
Adjacent sequences: A046927 A046928 A046929 * A046931 A046932 A046933


KEYWORD

nonn,easy,nice


AUTHOR

N. J. A. Sloane, Marc LeBrun


EXTENSIONS

More terms from Michel ten Voorde


STATUS

approved



