OFFSET
1,1
COMMENTS
Prime septuplets (p, p+2, p+6, p+8, p+12, p+18, p+20) are one of the two types of densest permissible constellations of 7 primes. Maximal gaps between septuplets of this type are listed in A201051; see more comments there.
LINKS
Alexei Kourbatov, Table of n, a(n) for n = 1..36
Tony Forbes, Prime k-tuplets
Alexei Kourbatov, Maximal gaps between prime septuplets
Alexei Kourbatov, Tables of record gaps between prime constellations, arXiv preprint arXiv:1309.4053, 2013.
Eric W. Weisstein, k-Tuple Conjecture
EXAMPLE
The gap of 165690 between septuplets starting at p=11 and p=165701 is the very first gap, so a(1)=11. The gap of 903000 between septuplets starting at p=165701 and p=1068701 is a maximal gap - larger than any preceding gap; therefore a(2)=165701. The next gap of 10831800 starts at p=1068701 and is again a maximal gap, so a(3)=1068701. The next gap is smaller, so it does not contribute to the sequence.
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Alexei Kourbatov, Nov 28 2011
STATUS
approved