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A235039
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Odd numbers which are factored to the same set of primes in Z as to the irreducible polynomials in GF(2)[X]; odd terms of A235036.
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4
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1, 111, 123, 219, 411, 511, 959, 1983, 2031, 3099, 3459, 3579, 4847, 5371, 6159, 7023, 7131, 7141, 7231, 7899, 7913, 8071, 8079, 9179, 12387, 12783, 13289, 15843, 26223, 27771, 28453, 28903, 31529, 31539, 39007, 45419, 49251, 49659, 51087, 53677, 56137, 57219, 61923
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OFFSET
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0,2
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COMMENTS
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These are odd nonprime numbers in A235032. After a(0)=1, the odd composite numbers in A235032.
The terms a(1) - a(42) are all semiprimes. Presumably terms with a larger number of prime factors also exist.
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LINKS
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EXAMPLE
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111 = 3*37. When these two prime factors (both terms of A091206), with binary representations '11' and '100101', are multiplied as:
100101
1001010
-------
1101111 = 111 in decimal
we see that the intermediate products 1*37 and 2*37 can be added together without producing any carry-bits (as they have no 1-bits in the same columns/bit-positions), so A048720(3,37) = 3*37 and thus 111 is included in this sequence.
Note that unlike in A235040, 15 = 3*5 is not included in this sequence, because its prime factor 5 is not in A091206, but instead decomposes further as A048720(3,3).
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PROG
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(define A235039 (MATCHING-POS 0 1 (lambda (n) (and (odd? n) (not (prime? n)) (equal? (ifactor n) (GF2Xfactor n))))))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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