OFFSET
3,1
COMMENTS
It is interesting that these primes occur rather frequently early on but gradually diminish as the iterations increase. Some ratios of count of twin primes p and the occurrence of prime(p) also a twin prime is as follows. Index< Ratio 1000 .74 10000 .48 100000 .39 1000000 .35 Looks like it is approaching a limit.
EXAMPLE
The 29th prime,109,is also a twin prime paired with the prime 107.
PROG
(PARI) twips(n) = { c1=0; c2=0; forprime(x=3, n, if(isprime(x+2), c1++); x1=prime(x); if(isprime(x-2) || isprime(x+2), if(isprime(x1-2) || isprime(x1+2), print1(x", "); c2++; ) ) ); print(); print(c2/c1+.0) }
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Oct 21 2003
STATUS
approved