OFFSET
1,1
COMMENTS
Conjecture. For n>=3, every a(n) is the lesser of a pair of cousin primes p and p+4, cf. A023200.
The limit of a(n) as n goes to infinity is infinity.
MATHEMATICA
Table[aPrime[[NestWhile[#1+1&, 1, !(nextAPrime[n aPrime[[#1]]]>n aPrime[[#1+1]])&]]], {n, 2, 20}]
PROG
(PARI) is_a025584(x) = isprime(x) && !isprime(x-2)
a025584_next(n) = {local(p); p=n+1; while(!is_a025584(p), p=p+1); p}
no_a025584(a, b) = {local(x, r); r=1; for(x=a+1, b-1, if(is_a025584(x), r=0)); r}
a207820(n) = {local(r, rp); rp=2; r=3; while(!no_a025584(n*rp, n*r), rp=r; r=a025584_next(r)); rp} \\ Michael B. Porter, Jan 20 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev and Peter J. C. Moses, Jan 10 2013
EXTENSIONS
a(21)-a(37) from Michael B. Porter, Jan 20 2013
STATUS
approved