

A321221


Numbers of the form 6n2 which are not a sum of two numbers that are the lesser of twin primes.


2



4, 94, 400, 514, 784, 904, 1114, 1144, 1264, 1354, 3244, 4204
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OFFSET

1,1


COMMENTS

Conjecture: This sequence is finite.
If this sequence is finite, then the Goldbach Strong Conjecture is true. If p1 and p2 are the lesser of twin primes, then q1=p1+2 and q2=p2+2 are also primes (they are the greater of twin primes). If 6n2 = p1+p2, then 6n = q1+p2 and 6n+2 = q1+q2.


LINKS

Table of n, a(n) for n=1..12.
Marcin Barylski, On 6k ± 1 Primes in Goldbach Strong Conjecture
Marcin Barylski, C++ program for generating A321221


EXAMPLE

a(1) = 4 because 4 = 2+2; there are no other Goldbach partitions and 2 is not the lesser of twin primes.
a(2) is not 6 because 6 = 3+3 and 3 is the lesser of twin primes.


MATHEMATICA

aQ[n_]:= (k=1; kmax=(n+2)/6; While[k<=kmax && !AllTrue[{6k1, 6k+1, 6(kmaxk)1, 6(kmaxk)+1}, PrimeQ], k++]; k>kmax); Select[6*Range[0, 10000]+4, aQ] (* Amiram Eldar, Nov 10 2018 *)


PROG

(PARI) ok(n)={if(n%6 == 4, forstep(k=3, n\2, 2, if(isprime(k) && isprime(k+2) && isprime(nk) && isprime(nk+2), return(0))); 1, 0)} \\ Andrew Howroyd, Nov 01 2018


CROSSREFS

Cf. A001359, A002375.
Sequence in context: A202899 A030246 A116160 * A116291 A061992 A221389
Adjacent sequences: A321218 A321219 A321220 * A321222 A321223 A321224


KEYWORD

nonn,more


AUTHOR

Marcin Barylski, Oct 31 2018


STATUS

approved



