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A070020 At these values of n the first, 2nd and 3rd cyclotomic polynomials all give prime numbers. 4
6, 12, 138, 150, 192, 348, 642, 1020, 1092, 1230, 1620, 1788, 1932, 2112, 2142, 2238, 2658, 2688, 2730, 3330, 3540, 3918, 4002, 4158, 5010, 5640, 6090, 6450, 6552, 6702, 7950, 8088, 9000, 9042, 9240, 9462, 9768, 10008, 10092, 10272, 10302, 10332 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Michael De Vlieger, Table of n, a(n) for n = 1..5000

FORMULA

n-1, n+1 and 1+n+n^2 are all primes.

EXAMPLE

n=6: 5,7 and 43 are prime values of first 3 cyclotomic polynomials

MATHEMATICA

psQ[n_]:=And@@PrimeQ[{n-1, n+1, n^2+n+1}]; Select[Range[11000], psQ] (* Harvey P. Dale, Nov 05 2011 *)

Select[Range[10500], AllTrue[Cyclotomic[Range@ 3, #], PrimeQ] &] (* Michael De Vlieger, Dec 08 2018 *)

CROSSREFS

Cf. A070155-A070157, A000068, A006313-A006316, A056993-A056995, A005574, A057465, A057002, A070025, A070042.

Sequence in context: A102062 A164584 A156432 * A308565 A203754 A002922

Adjacent sequences:  A070017 A070018 A070019 * A070021 A070022 A070023

KEYWORD

easy,nonn

AUTHOR

Labos Elemer, May 07 2002

STATUS

approved

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Last modified August 26 05:23 EDT 2019. Contains 326328 sequences. (Running on oeis4.)