This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A260428 Composite numbers whose binary representations encode a polynomial (with coefficients 0 or 1) which is irreducible over Q, but reducible over GF(2). 4
 69, 77, 81, 121, 169, 205, 209, 261, 265, 275, 289, 295, 305, 321, 323, 327, 329, 339, 377, 405, 407, 437, 453, 473, 475, 481, 493, 517, 533, 551, 553, 559, 565, 575, 581, 583, 595, 625, 649, 667, 671, 689, 703, 707, 737, 747, 749, 755, 763, 767, 779, 781, 785, 805, 815, 833, 835, 851, 855, 861, 869, 893, 905 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Antti Karttunen, Table of n, a(n) for n = 1..11585 MAPLE f:= proc(n) local L, p, x;   if isprime(n) then return false fi;   L:= convert(n, base, 2);   p:= add(L[i]*x^(i-1), i=1..nops(L));   irreduc(p) and not (Irreduc(p) mod 2); end proc: select(f, [\$2..10000]); # Robert Israel, Jul 27 2015 PROG (PARI) isA260428(n) = (polisirreducible( Pol(binary(n)) ) && !polisirreducible(Pol(binary(n))*Mod(1, 2)) && !isprime(n)); n = 0; i = 0; while(n < 65537, n++; if(isA260428(n), i++; write("b260428.txt", i, " ", n))); CROSSREFS Intersection of A002808 and A260427. Intersection of A091212 and A206074. Intersection of A091242 and A206075. Complement of A257688 in A206074. Sequence in context: A166067 A253437 A325386 * A168477 A264045 A295806 Adjacent sequences:  A260425 A260426 A260427 * A260429 A260430 A260431 KEYWORD nonn AUTHOR Antti Karttunen, Jul 26 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 10 12:43 EST 2019. Contains 329896 sequences. (Running on oeis4.)