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A046930 Size of sea of composite numbers surrounding n-th prime.

%I A046930 #22 Dec 21 2021 23:46:56
%S A046930 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,
%T A046930 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,
%U A046930 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
%N A046930 Size of sea of composite numbers surrounding n-th prime.
%H A046930 T. D. Noe, <a href="/A046930/b046930.txt">Table of n, a(n) for n = 1..10000</a>
%F A046930 a(n) = A031131(n) - 2 for n > 1. - _Reinhard Zumkeller_, Dec 19 2013
%e A046930 23 is in a sea of 8 composites: 20,21,22,23,24,25,26,27,28.
%p A046930 [ seq(ithprime(i)-ithprime(i-2)-2,i=3..100) ];
%t A046930 Table[ Prime[n + 2] - Prime[n] - 2, {n, 75}] (* _Robert G. Wilson v_ Oct 27 2004 *)
%t A046930 Join[{1},#[[3]]-#[[1]]-2&/@Partition[Prime[Range[90]],3,1]] (* _Harvey P. Dale_, Sep 26 2012 *)
%o A046930 (Haskell)
%o A046930 a046930 1 = 1
%o A046930 a046930 n = subtract 2 $ a031131 n  -- _Reinhard Zumkeller_, Dec 19 2013
%Y A046930 Related sequences: A023186-A023188, A046929-A046931, A051650, A051652, A051697-A051702, A051728-A051730.
%K A046930 nonn,easy,nice
%O A046930 1,3
%A A046930 _N. J. A. Sloane_, _Marc LeBrun_
%E A046930 More terms from _Michel ten Voorde_