OFFSET
1,1
COMMENTS
Let p be a prime and let i be the index of p in A000040. Then p is a term of this sequence if both p and i are terms of A051003, or, equivalently, if i is a term of A051003 and p is a term of A131645.
Conjecture 1: The sequence is infinite.
An argument in favor of the conjecture goes as follows: Choose any sufficiently large integer i containing the substring "666". Then it seems very likely, assuming the digits of prime(i) are distributed uniformly, that prime(i) contains the substring "666" at least once.
Based on that argument, one can make the following stronger conjecture:
Conjecture 2: There exists an integer h such that for each i >= h, prime(A051003(i)) is a term of the sequence.
EXAMPLE
836663 is prime(66651). Both the prime and its prime index contain the substring "666" in their decimal representation, so 836663 is a term of the sequence.
PROG
(PARI) is(n) = my(bst=[6, 6, 6], d=digits(n), e=digits(primepi(n))); for(x=1, #e-2, my(v=[e[x], e[x+1], e[x+2]]); if(v==bst, for(y=1, #d-2, my(w=[d[y], d[y+1], d[y+2]]); if(w==bst, return(1))))); 0
forprime(p=1, , if(is(p), print1(p, ", ")))
CROSSREFS
KEYWORD
nonn,base,less
AUTHOR
Felix Fröhlich, Jun 10 2018
EXTENSIONS
a(7)-a(26) from Giovanni Resta, Jun 11 2018
STATUS
approved