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A161562
Even numbers n such that { n-p ; p prime, 2 < p < n/2 } contains at least twice as many primes as composites.
0
2, 4, 6, 8, 10, 16, 18, 20, 22, 24, 36, 60, 84, 90, 114, 120, 210, 420
OFFSET
1,1
COMMENTS
It seems that this sequence is finite, and that 420 is the largest term. [M. F. Hasler, Nov 11 2009]
EXAMPLE
16-3=13,16-5=11.(primes:2 times) 16-7=9.(composite:1 time);
24-5=19,24-7=17,24-11=13.(primes:3 times) 24-3=21.(composite:1 time);
90-3=87,90-7=83,90-11=79,90-17=73,90-19-71,90-23=67,90-29=61,90-31=59,90-37=53,90-43=47.(primes:10 times) 90-5=85,90-13=77,90-41=49.(composite:3 times),..
PROG
(PARI) {for(n=1, 1e6, my(s=0); forprime( p=3, n-1, s+=if( isprime(2*n-p), 1, -2)); s>=0 & print1(2*n", "))} \\ M. F. Hasler, Nov 11 2009
CROSSREFS
Sequence in context: A338738 A345986 A226809 * A333019 A102470 A057195
KEYWORD
nonn,fini,full
AUTHOR
EXTENSIONS
Reworded definition and initial terms added by M. F. Hasler, Nov 11 2009
Definition reworded by Harvey P. Dale, Sep 17 2023
STATUS
approved