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A152050
Smallest lower twin prime tp such that p + tp + 1 is prime. p ranges over the prime numbers.
0
3, 5, 3, 5, 3, 5, 3, 5, 11, 5, 3, 5, 3, 5, 5, 11, 5, 3, 11, 5, 3, 5, 11, 3, 5, 3, 5, 3, 17, 3, 5, 11, 11, 17, 5, 5, 3, 5, 5, 11, 11, 5, 3, 29, 11, 11, 3, 5, 3, 5, 11, 29, 5, 5, 5, 11, 5, 3, 11, 29, 17, 3, 5, 3, 29, 5, 11, 5, 3, 5, 29, 5, 5, 3, 5, 11, 3, 17, 11, 11, 11, 11, 5, 3, 5, 11, 3, 5, 3, 11
OFFSET
1,1
COMMENTS
Conjecture: For all primes p <= n there is always a lower twin prime L less than n such that p+L+1 is prime.
EXAMPLE
29 is the 9th odd prime. 29+3+1, 29+5+1 are not prime. 29+11+1 is prime, so a(9) = 11 the smallest lower twin prime satisfying the definition for prime 29.
PROG
(PARI) g(n) = ct=0; for(x=2, n, p1=prime(x); for(y=1, n, p2=twinl(y); z=p1+p2+1;
if(isprime(z), ct++; print1(p2", "); break))); ct
CROSSREFS
Sequence in context: A214287 A010703 A107489 * A103506 A094929 A096634
KEYWORD
nonn
AUTHOR
Cino Hilliard, Nov 21 2008
STATUS
approved