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A023188 Lonely (or isolated) primes: least prime of distance n from nearest prime (n = 1 or even). 18

%I #21 Dec 01 2020 03:28:14

%S 2,5,23,53,409,293,211,1847,3137,2179,3967,23719,16033,40387,44417,

%T 24281,158699,220973,172933,321509,38501,58831,203713,268343,206699,

%U 829399,824339,413353,2280767,2305549,3253631,1272749,2401807,2844833,3021241

%N Lonely (or isolated) primes: least prime of distance n from nearest prime (n = 1 or even).

%C a(1)=least prime of distance 1 from nearest prime.

%C if n>1 a(n)=least prime of distance 2n-2 from nearest prime.

%H Giovanni Resta, <a href="/A023188/b023188.txt">Table of n, a(n) for n = 1..191</a> (first 65 terms from Daniel Lignon)

%H Abhimanyu Kumar and Anuraag Saxena, <a href="https://arxiv.org/abs/2011.14210">Insulated primes</a>, arXiv:2011.14210 [math.NT], 2020. Mentions this sequence.

%t NextPrim[n_] := Block[{k = n + 1}, While[ !PrimeQ[k], k++ ]; k]; a = Table[0, {35}]; p = 2; q = 3; k = 1; Do[r = NextPrim[q]; m = Min[r - q, q - p]/2; If[m < 35 && a[[m]] == 0, a[[m]] = q]; p = q; q = r, {n, 1, 235000}]

%t Join[{2},Transpose[Flatten[Table[Select[Partition[Prime[ Range[ 1000000]],3,1], Min[ Differences[#]] == 2n&,1],{n,40}],1]][[2]]](* _Harvey P. Dale_, Nov 17 2013 *)

%Y Related sequences: A023186-A023188, A046929-A046931, A051650, A051652, A051697-A051702, A051728-A051730.

%K nonn

%O 1,1

%A _David W. Wilson_

%E a(36)-a(65) from _Daniel Lignon_, Aug 07 2015

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Last modified March 29 00:26 EDT 2024. Contains 371264 sequences. (Running on oeis4.)