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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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified January 17 23:37 EST 2020. Contains 330995 sequences. (Running on oeis4.)