

A088212


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


2



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, 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, 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
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OFFSET

1,1


COMMENTS

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


LINKS

Zak Seidov, Table of n, a(n) for n = 1..10000


EXAMPLE

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


MATHEMATICA

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


CROSSREFS

Cf. A088213.
Sequence in context: A235669 A118088 A298211 * A085208 A257302 A268715
Adjacent sequences: A088209 A088210 A088211 * A088213 A088214 A088215


KEYWORD

easy,nonn


AUTHOR

Zak Seidov, Sep 23 2003


STATUS

approved



