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A107220
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Numbers n so that 1 + (x + x^3 + x^5 + x^7 + ...+ x^(2*n+1)) is irreducible over GF(2).
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0
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1, 3, 5, 7, 9, 13, 23, 27, 31, 37, 63, 69, 117, 119, 173, 219, 223, 247, 307, 363, 383, 495, 695, 987
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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LINKS
| Joerg Arndt, fxtbook, section 40.9.10 "Irreducible alternating polynomials", pp.853
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EXAMPLE
| The number 5 is in the sequence because x^11 + x^9 + x^7 + x^5 + x^3 + x + 1 is irreducible over GF(2) (and 11=2*5+1)
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PROG
| (PARI) for(d=1, 1000, p=(1+sum(t=0, d, x^(2*t+1))); if(polisirreducible(Mod(1, 2)*p), print1(d, ", ")));
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CROSSREFS
| Sequence in context: A089228 A133847 A134180 * A098758 A029608 A145388
Adjacent sequences: A107217 A107218 A107219 * A107221 A107222 A107223
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KEYWORD
| nonn,more
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AUTHOR
| Joerg Arndt (arndt(AT)jjj.de), Jun 08 2005
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EXTENSIONS
| More terms by Joerg, Apr 2 2011
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