A136240 Numbers n among A006093 such that n^2 + n + 1 is prime.
1, 2, 6, 12, 66, 78, 138, 150, 162, 192, 336, 348, 378, 456, 540, 612, 642, 726, 768, 918, 990, 1020, 1092, 1116, 1200, 1230, 1380, 1422, 1548, 1566, 1596, 1620, 1692, 1746, 1788, 1800, 1932, 1986, 2010, 2016, 2112, 2136, 2142, 2238, 2280, 2556, 2646
Offset: 1
Keywords
Links
- Harvey P. Dale, Table of n, a(n) for n = 1..1000
Crossrefs
Cf. A136241.
Programs
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Mathematica
Select[Prime[Range[400]]-1,PrimeQ[#^2+#+1]&] (* Harvey P. Dale, Feb 11 2022 *)
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PARI
isA136240(n) = {isprime(n+1) && isprime(n^2+n+1)} \\ Michel Marcus, Jul 28 2013
Formula
a(n) = A065508(n) - 1.
Comments