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Old 2019-04-16, 22:11   #6
Pietro Maiorana
 
Feb 2019

3 Posts
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(Start)
A100319+1 (Even numbers m such that at least one of m-1 and m+1 is composite)
can be obtained as the union of:

3*A005818;

5*A038179 without 2;


7*A007310 without 1;


A038511


A025584 without 2, 3. (End)

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The sequence A038511 can be obtained by multiplying each term of A008364 , except {1}, by itself and by all subsequent terms. Rewrite the terms in ascending order.

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(Start)
To obtain A025584 (Primes p such that p-2 is not a prime):
Write all terms of the form 2k + 7 and delete all terms of the form (6k + (-1) ^ k + 13)/2 [without A121764] and all terms of A092256
Finally, add 2 and 3.
(End)



To calculate A121764 (Single, or isolated or non-twin primes of form 6n + 1)
consider all term of A092256(n) + 2 except those in common with:
A038511, 5*A038179, and 7*A007310.



A092256 (Nonprimes of form 6k+5) is the union of:
numbers of the form 5*(6k + 1) , numbers of the form 7*(6k + 5), and terms of A038511 of the form 3*k+2
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Last fiddled with by Pietro Maiorana on 2019-04-16 at 22:15
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