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A305419 Largest k < n whose binary expansion encodes an irreducible (0,1)-polynomial over GF(2)[X], with a(1) = a(2) = 1. 10
1, 1, 2, 3, 3, 3, 3, 7, 7, 7, 7, 11, 11, 13, 13, 13, 13, 13, 13, 19, 19, 19, 19, 19, 19, 25, 25, 25, 25, 25, 25, 31, 31, 31, 31, 31, 31, 37, 37, 37, 37, 41, 41, 41, 41, 41, 41, 47, 47, 47, 47, 47, 47, 47, 47, 55, 55, 55, 55, 59, 59, 61, 61, 61, 61, 61, 61, 67, 67, 67, 67, 67, 67, 73, 73, 73, 73, 73, 73, 73, 73, 73, 73, 73, 73, 73, 73, 87 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

For n >= 3, a(n) is the largest term of A014580 less than n.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..21845

Index entries for sequences related to polynomials in ring GF(2)[X]

PROG

(PARI)

A091225(n) = polisirreducible(Pol(binary(n))*Mod(1, 2));

A305419(n) = if(n<3, 1, my(k=n-1); while(k>1 && !A091225(k), k--); (k));

CROSSREFS

Cf. A014580, A091225, A305420, A305422.

Cf. also A151799 (A136548), A305429.

Sequence in context: A200924 A111913 A210796 * A075757 A096420 A096193

Adjacent sequences:  A305416 A305417 A305418 * A305420 A305421 A305422

KEYWORD

nonn

AUTHOR

Antti Karttunen, Jun 07 2018

STATUS

approved

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Last modified June 24 17:51 EDT 2021. Contains 345419 sequences. (Running on oeis4.)