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A090693 Positive numbers n such that n^2 - 2n + 2 is a prime. 7

%I

%S 2,3,5,7,11,15,17,21,25,27,37,41,55,57,67,75,85,91,95,111,117,121,125,

%T 127,131,135,147,151,157,161,171,177,181,185,205,207,211,225,231,237,

%U 241,251,257,261,265,271,281,285,301,307,315,327,341,351,385,387,397

%N Positive numbers n such that n^2 - 2n + 2 is a prime.

%D M. Cerasoli, F. Eugeni and M. Protasi, Elementi di Matematica Discreta, Bologna 1988

%D Emanuele Munarini and Norma Zagaglia Salvi, Matematica Discreta,UTET, CittaStudiEdizioni, Milano 1997

%H Peter J. C. Moses, <a href="/A090693/b090693.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A005574(n)+1.

%t a={};Do[If[PrimeQ[n^2-2n+2],AppendTo[a,n]],{n,1000}];a (* _Peter J. C. Moses_, Apr 02 2013 *)

%t Select[Range[400],PrimeQ[#^2-2#+2]&] (* _Harvey P. Dale_, May 10 2013 *)

%o (Python)

%o # Python 3.2 or higher required.

%o from itertools import accumulate

%o from sympy import isprime

%o 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

%Y A002496 gives primes, A062325 gives prime index. Cf. A001912.

%Y A005574(n+1) + 1.

%K easy,nonn

%O 1,1

%A _Giovanni Teofilatto_, Dec 19 2003

%E Corrected and extended by _Ray Chandler_, Dec 28 2003

%E Definition corrected by _Chai Wah Wu_, Sep 23 2014

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Last modified January 18 20:19 EST 2018. Contains 297865 sequences.