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 A090693 Positive numbers n such that n^2 - 2n + 2 is a prime. 7
 2, 3, 5, 7, 11, 15, 17, 21, 25, 27, 37, 41, 55, 57, 67, 75, 85, 91, 95, 111, 117, 121, 125, 127, 131, 135, 147, 151, 157, 161, 171, 177, 181, 185, 205, 207, 211, 225, 231, 237, 241, 251, 257, 261, 265, 271, 281, 285, 301, 307, 315, 327, 341, 351, 385, 387, 397 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 REFERENCES M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988 Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta,UTET, CittaStudiEdizioni, Milano 1997 LINKS Peter J. C. Moses, Table of n, a(n) for n = 1..10000 FORMULA a(n) = A005574(n)+1. MATHEMATICA a={}; Do[If[PrimeQ[n^2-2n+2], AppendTo[a, n]], {n, 1000}]; a (* Peter J. C. Moses, Apr 02 2013 *) Select[Range[400], PrimeQ[#^2-2#+2]&] (* Harvey P. Dale, May 10 2013 *) PROG (Python) # Python 3.2 or higher required. from itertools import accumulate from sympy import isprime A090693_list = [i for i, n in enumerate(accumulate(range(10**5), lambda x, y:x+2*y-3)) if i > 0 and isprime(n+2)] # Chai Wah Wu, Sep 23 2014 CROSSREFS A002496 gives primes, A062325 gives prime index. Cf. A001912. A005574(n+1) + 1. Sequence in context: A182803 A106532 A240556 * A260794 A277576 A260164 Adjacent sequences: A090690 A090691 A090692 * A090694 A090695 A090696 KEYWORD easy,nonn AUTHOR Giovanni Teofilatto, Dec 19 2003 EXTENSIONS Corrected and extended by Ray Chandler, Dec 28 2003 Definition corrected by Chai Wah Wu, Sep 23 2014 STATUS approved

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Last modified June 3 13:22 EDT 2023. Contains 363110 sequences. (Running on oeis4.)