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A242046 Least integer k > n + 1 such that n^2 + (n + 1)^2 + k^2 is prime. 1
2, 6, 4, 6, 24, 14, 8, 12, 16, 24, 24, 14, 14, 24, 16, 20, 42, 20, 26, 54, 30, 26, 30, 28, 26, 54, 42, 38, 42, 34, 40, 48, 38, 36, 36, 44, 48, 102, 42, 46, 54, 44, 50, 48, 60, 54, 66, 50, 54, 54, 54, 54, 54, 56, 64, 84, 58, 62, 84, 64, 66, 78, 64, 66, 84, 74 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

COMMENTS

If n is in A027863 then a(n) = n + 2, otherwise a(n) > n + 2. All terms are even. Corresponding primes are 5, 41, 29, 61, 617, ...

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 0..10000

MATHEMATICA

lk[n_]:=Module[{k=n+2, c=n^2+(n+1)^2}, While[!PrimeQ[c+k^2], k++]; k]; Array[ lk, 70, 0] (* Harvey P. Dale, Aug 06 2015 *)

PROG

(PARI) a(n)=k=n+2; while(!isprime(n^2+(n+1)^2+k^2), k++); k

vector(100, n, a(n-1)) \\ Jens Kruse Andersen, Aug 26 2014

CROSSREFS

Cf. A027863.

Sequence in context: A247566 A151689 A216833 * A330776 A327458 A202347

Adjacent sequences:  A242043 A242044 A242045 * A242047 A242048 A242049

KEYWORD

nonn

AUTHOR

Zak Seidov, Aug 24 2014

EXTENSIONS

Corrected and extended by Jens Kruse Andersen, Aug 26 2014

STATUS

approved

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Last modified January 17 12:06 EST 2022. Contains 350394 sequences. (Running on oeis4.)