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A088212 Smallest k>1 such that n+k^2 is prime. 2

%I

%S 2,3,2,3,6,5,2,3,2,3,6,5,2,3,2,5,6,5,2,3,4,3,6,7,2,9,2,3,12,7,4,3,2,3,

%T 6,5,2,3,2,7,24,5,2,3,4,5,6,5,2,3,4,3,6,5,2,9,2,3,18,7,6,3,2,3,6,25,2,

%U 9,2,3,6,5,4,3,2,5,6,5,2,3,4,5,12,5,2,9,4,3,12,7,4,3,2,3,6,19,2,3,2,3,6,5,2

%N Smallest k>1 such that n+k^2 is prime.

%C Conjecture: all integers >1 eventually appear. Among first 300000 terms, first absent integers are 113, 119, 122, 124, 127, 130, 134, 136, 137, 139, 140, 142, 143, 145, 146, 148, 149, 151, 152, 154, 155, 157, 158, 160, 161, 163, 164, 166, 167, 169, 170, 172, 173, 175, 176, 178, 179, 181, 182, 184, 185, 186, 187, 188, 190, 191, 193, 194, 196, 197, 199, 200. - _Zak Seidov_, Jun 06 2013

%H Zak Seidov, <a href="/A088212/b088212.txt">Table of n, a(n) for n = 1..10000</a>

%e n=1: 1+2^2=5; n=5: 5+6^2=41.

%t k[n_]:=Module[{k=2},While[!PrimeQ[n+k^2],k++];k]; Array[k,110] (* _Harvey P. Dale_, Aug 19 2011 *)

%Y Cf. A088213.

%K easy,nonn

%O 1,1

%A _Zak Seidov_, Sep 23 2003

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Last modified February 18 04:48 EST 2020. Contains 332011 sequences. (Running on oeis4.)