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A215248 Numbers n such that n^2 + 1 and (n^2+2)/6 are both primes. 2
4, 10, 16, 20, 26, 56, 110, 116, 170, 224, 236, 314, 326, 340, 430, 584, 700, 764, 920, 946, 1054, 1106, 1276, 1294, 1406, 1546, 1550, 1654, 1684, 1700, 1756, 1766, 1784, 1816, 2006, 2026, 2116, 2260, 2294, 2314, 2320, 2360, 2576, 2600, 2684, 2746, 2770, 2924 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n==2 or 4 (mod 6) so that (n^2+2)/6 is an integer. - Robert Israel, May 03 2017

LINKS

Robert Israel, Table of n, a(n) for n = 1..10000

EXAMPLE

4 is in the sequence because 4^2+1 = 17 and (4^2+2)/6 = 3 are both primes.

MAPLE

select(t -> isprime(t^2+1) and isprime((t^2+2)/6), [seq(seq(6*j+k, k=[2, 4]), j=0..1000)]); # Robert Israel, May 03 2017

MATHEMATICA

Select[Range[3000], PrimeQ[(#^2+1)]&&PrimeQ[(#^2+2)/6]&]

CROSSREFS

Cf. A005574, A002496.

Sequence in context: A310503 A310504 A310505 * A310506 A310507 A334115

Adjacent sequences:  A215245 A215246 A215247 * A215249 A215250 A215251

KEYWORD

nonn

AUTHOR

Michel Lagneau, Aug 10 2012

STATUS

approved

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Last modified July 6 11:37 EDT 2022. Contains 355110 sequences. (Running on oeis4.)