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 A060800 a(n) = p^2 + p + 1 where p runs through the primes. 21
 7, 13, 31, 57, 133, 183, 307, 381, 553, 871, 993, 1407, 1723, 1893, 2257, 2863, 3541, 3783, 4557, 5113, 5403, 6321, 6973, 8011, 9507, 10303, 10713, 11557, 11991, 12883, 16257, 17293, 18907, 19461, 22351, 22953, 24807, 26733, 28057, 30103, 32221 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Terms are divisible by 3 iff p is of the form 6*m+1 (A002476). - Michel Marcus, Jan 15 2017 LINKS Harry J. Smith, Table of n, a(n) for n = 1..1000 FORMULA a(n) = A036690(n) + 1. a(n) = 1 + A008864(n)*A000040(n) = (A030078(n) - 1)/A006093(n). - Reinhard Zumkeller, Aug 06 2007 a(n) = sigma(prime(n)^2) = A000203(A000040(n)^2). - Zak Seidov, Feb 13 2016 a(n) = A000203(A001248(n)). - Michel Marcus, Feb 15 2016 EXAMPLE a(3)=31 because 5^2 + 5 + 1 = 31. MAPLE A060800:= n -> map (p -> p^(2)+p+1, ithprime(n)): seq (A060800(n), n=1..41); # Jani Melik, Jan 25 2011 MATHEMATICA #^2 + # + 1&/@Prime[Range[200]] (* Vincenzo Librandi, Mar 20 2014 *) PROG (PARI) { n=0; forprime (p=2, prime(1000), write("b060800.txt", n++, " ", p^2 + p + 1); ) } \\ Harry J. Smith, Jul 13 2009 (MAGMA) [p^2+p+1: p in PrimesUpTo(200)]; // Vincenzo Librandi, Mar 20 2014 CROSSREFS Cf. A001248, A131991, A131992, A131993. Cf. A008864, A000203. - Zak Seidov, Feb 13 2016 Sequence in context: A031158 A301683 A091431 * A272204 A107146 A201601 Adjacent sequences:  A060797 A060798 A060799 * A060801 A060802 A060803 KEYWORD nonn,easy AUTHOR Jason Earls, Apr 27 2001 EXTENSIONS More terms from Larry Reeves (larryr(AT)acm.org), May 03 2001 STATUS approved

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Last modified October 22 12:30 EDT 2019. Contains 328318 sequences. (Running on oeis4.)