login
A267721
a(n) is the least term of A030461 with gap = 6*n between consecutive primes or 0 if no such term exists.
2
3137, 199211, 523541, 16691693, 1393313963, 2428124317, 3498135023, 7318973237, 4028940343, 191353191413, 221327221393, 507217507289, 937253937331, 10402271040311, 843911844001, 25654632565559, 81661078166209, 55778515577959, 82237498223863
OFFSET
1,1
COMMENTS
Subsequence of A030461.
a(n) is the concatenation of the smallest prime p and the next prime q, such that p + 6n = q and the concatenations of these 2 primes is also prime. a(n) = 0 if no such term exists.
LINKS
EXAMPLE
a(1) = A030461(2) = 3137. gap = 37 - 31 = 6 = 6 * 1.
a(2) = 199211, because 199211 is the first term in A030461, with gap = 211 - 199 = 12 = 6 * 2.
MAPLE
Primes:= select(isprime, [seq(i, i=3..10^7, 2)]):
cati:= (x, y) -> 10^(1+ilog10(y))*x+y;
for i from 1 to nops(Primes)-1 do
g:= Primes[i+1]-Primes[i];
if g mod 6 <> 0 then next fi;
if assigned(A[g/6]) then next fi;
z:= cati(Primes[i], Primes[i+1]);
if isprime(z) then A[g/6]:= z fi;
od:
seq(A[i], i=1..max(map(op, [indices(A)]))); # Robert Israel, Jan 24 2016
CROSSREFS
KEYWORD
base,nonn
AUTHOR
Jean-Marc Rebert, Jan 20 2016
STATUS
approved