A305429 - OEIS

A305429

Largest k < n whose binary expansion encodes an irreducible (0,1)-polynomial over Q, with a(1) = a(2) = 1.

1, 1, 2, 3, 3, 5, 5, 7, 7, 7, 7, 11, 11, 13, 13, 13, 13, 17, 17, 19, 19, 19, 19, 23, 23, 25, 25, 25, 25, 29, 29, 31, 31, 31, 31, 31, 31, 37, 37, 37, 37, 41, 41, 43, 43, 43, 43, 47, 47, 47, 47, 47, 47, 53, 53, 55, 55, 55, 55, 59, 59, 61, 61, 61, 61, 61, 61, 67, 67, 69, 69, 71, 71, 73, 73, 73, 73, 77, 77, 79, 79, 81, 81, 83, 83, 83, 83, 87, 87

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OFFSET

1,3

COMMENTS

For n >= 3, a(n) is the largest term of A206074 less than n.

LINKS

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

PROG

(PARI)

A257000(n) = polisirreducible(Pol(binary(n)));

A305429(n) = if(n<3, 1, my(k=n-1); while(k>1 && !A257000(k), k--); (k));

CROSSREFS