This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A002384 Numbers n such that n^2 + n + 1 is prime. (Formerly M0626 N0228) 68
 1, 2, 3, 5, 6, 8, 12, 14, 15, 17, 20, 21, 24, 27, 33, 38, 41, 50, 54, 57, 59, 62, 66, 69, 71, 75, 77, 78, 80, 89, 90, 99, 101, 105, 110, 111, 117, 119, 131, 138, 141, 143, 147, 150, 153, 155, 161, 162, 164, 167, 168, 173, 176, 188, 189, 192, 194, 203, 206, 209, 215 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Damianou, p. 4, claims that there is strong experimental evidence that n^2+n+1 is prime for infinitely many values of n. There are a total of 189 such values under 1000. - Jonathan Vos Post, Jan 06 2011 A002383 lists the corresponding primes. - Bernard Schott, Dec 22 2012 This is also the list of bases where 111 represents a prime number. - Christian N. K. Anderson, Mar 28 2013 If d>1 divides n^2 + n + 1, then n + k*d is not in the sequence, for all k>=1. - Gionata Neri, Mar 04 2017 REFERENCES A. J. C. Cunningham, Binomial Factorisations, Vols. 1-9, Hodgson, London, 1923-1929; see Vol. 1, pp. 245-259. D. H. Lehmer, Guide to Tables in the Theory of Numbers. Bulletin No. 105, National Research Council, Washington, DC, 1941, p. 46. L. Poletti, Le serie dei numeri primi appartenente alle due forme quadratiche (A) n^2+n+1 e (B) n^2+n-1 per l'intervallo compreso entro 121 milioni, e cioè per tutti i valori di n fino a 11000, Atti della Reale Accademia Nazionale dei Lincei, Memorie della Classe di Scienze Fisiche, Matematiche e Naturali, s. 6, v. 3 (1929), pages 193-218. N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence). N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence). LINKS T. D. Noe and Zak Seidov, Table of n, a(n) for n = 1..10000 (First 1000 terms from T. D. Noe) A. J. C. Cunningham, Binomial Factorisations, Vols. 1-9, Hodgson, London, 1923-1929. [Annotated scans of a few pages from Volumes 1 and 2] Pantelis A. Damianou, On prime values of cyclotomic polynomials, arXiv:1101.1152 [math.NT], Jan 06 2011. Oliver Knill, Goldbach for Gaussian, Hurwitz, Octavian and Eisenstein primes, arXiv preprint arXiv:1606.05958 [math.NT], 2016. Oliver Knill, Some experiments in number theory, arXiv preprint arXiv:1606.05971 [math.NT], 2016. FORMULA a(n) = (A088503(n) - 1)/2. - Ray Chandler MATHEMATICA Select[Range@ 216, PrimeQ[#^2 + # + 1] &] (* Michael De Vlieger, Mar 06 2017 *) PROG (MAGMA)[ n: n in [1..300] | IsPrime(n^2+n+1)] // Vincenzo Librandi, Nov 21 2010 (PARI) is(n)=isprime(n^2+n+1) \\ Charles R Greathouse IV, Jan 21 2014 CROSSREFS Cf. A002383, A049407, A049408, A075723, A088503, A110284. Sequence in context: A120768 A271109 A293033 * A096176 A002243 A094763 Adjacent sequences:  A002381 A002382 A002383 * A002385 A002386 A002387 KEYWORD nonn,easy AUTHOR EXTENSIONS Extended by Ray Chandler, Sep 07 2005 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 14 14:50 EST 2019. Contains 329979 sequences. (Running on oeis4.)