

A152451


From every interval (2^(m1), 2^m), we remove primes p for which 2^mp is a prime; the sequence gives the remaining odd primes.


8



3, 7, 17, 23, 31, 37, 43, 71, 73, 79, 83, 89, 101, 103, 107, 113, 127, 131, 137, 139, 151, 157, 163, 179, 181, 191, 193, 199, 211, 223, 229, 241, 257, 263, 269, 277, 281, 293, 307, 311, 317, 337, 347, 353, 359, 367, 379, 383, 389, 397, 401, 419, 421, 431, 443
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OFFSET

1,1


COMMENTS

Powers of 2 are not expressible as sums of two primes from this sequence.
Consider a strong Goldbach conjecture: every even number n >= 6 is a sum of two primes, the lesser of which is O((log(n))^2*log(log(n))) (cf. comment to A152522). The number of such representations for 2^k, trivially, is less than k^5 for k > k_0. Removing the maximal primes in every such representation of 2^k, k >= 3, we obtain an analog B of A152451 with the counting function H(x) = pi(x)  O((log(x))^5). Replacing in B the first N terms with N consecutive primes (with arbitrarily large N), we obtain a sequence which essentially is indistinguishable from the sequence of all primes with the help of the approximation of pi(x) by li(x), since, according to the wellknown Littlewood result, the remainder term in the theorem of primes cannot be less than sqrt(x)logloglog(x)/log(x). But for this sequence we have infinitely many even numbers for which the considered strong Goldbach conjecture is wrong. Thus the conjecture is essentially unprovable.


LINKS

Table of n, a(n) for n=1..55.


FORMULA

If A(X) is the counting function for the terms a(n)<=x, then A(x) = x/log(x) + O(x*log(log(x))/(log(x))^2).


PROG

(PARI) lista(nn) = {forprime(p=3, nn, m = ceil(log(p)/log(2)); if ((m<3)  !isprime(2^mp), print1(p, ", ")); ); } \\ Michel Marcus, Sep 12 2015


CROSSREFS

Sequence in context: A018411 A083989 A277213 * A097958 A118940 A127175
Adjacent sequences: A152448 A152449 A152450 * A152452 A152453 A152454


KEYWORD

nonn


AUTHOR

Vladimir Shevelev, Dec 04 2008, Dec 05 2008, Dec 08 2008, Dec 12 2008


STATUS

approved



