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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 January 20 10:36 EST 2018. Contains 297960 sequences.