This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
The gap of 165690 between septuplets starting at p=11 and p=165701 is the very first gap, so a(1)=165690. 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)=903000. The next gap of 10831800 is again a maximal gap, so a(3)=10831800. The next gap is smaller, so it does not contribute to the sequence.
The gap of 83160 between septuplets starting at p=5639 and p=88799 is the very first gap, so a(1)=83160. The gap of 195930 between septuplets starting at p=88799 and p=284729 is a maximal gap - larger than any preceding gap; therefore a(2)=195930. The next gap of 341880 is again a maximal gap, so a(3)=341880. The next gap is smaller, so it does not contribute to the sequence.
a(0) = 0 because no single-digit prime starts a prime septuplet.
a(1) = 1 because 10^1 + 1 = 11 = A022009(1) is the first member of the smallest (2-digit) prime septuplet {11, 13, 17, 19, 23, 29, 31} (of the first type).
a(2) = 0 because there is no prime septuplet starting with a 3-digit prime.
a(3) = 4639 because 10^3 + a(3) = 5639 = A022010(1) is the first 4-digit initial member of a prime septuplet, which happens to be of the second type, D = {0, 2, 8, 12, 14, 18, 20}. Similarly, 10^4 + a(4) = 88799 = A022010(2) starts the smallest 5-digit prime septuplet.
For all subsequent terms, a(n) < 10^n (conjectured), so the primes are of the form 10...0XXX where XXX = a(n).
apply( {A343637(n,D=[2,6,8,12,14,18,20],X=2^6+2^14)=forprime(p=10^n, 10^(n+1), my(t=2); foreach(D, d, ispseudoprime(p+d)||(t-- && bittest(X,d))||next(2));return(p-10^n))}, [0..10]) \\ For illustration; unoptimized code, becomes slow for n >= 11.
The irregular triangle begins: 0, 2 0, 2, 6, 0, 4, 6 0, 2, 6, 8 0, 2, 6, 8, 12, 0, 4, 6, 10, 12 0, 4, 6, 10, 12, 16 0, 2, 6, 8, 12, 18, 20, 0, 2, 8, 12, 14, 18, 20
The gap of 83160 between septuplets starting at p=5639 and p=88799 is the very first gap, so a(1)=5639. The gap of 195930 between septuplets starting at p=88799 and p=284729 is a maximal gap - larger than any preceding gap; therefore a(2)=88799. The next gap starts at p=284729 and is again a maximal gap, so a(3)=284729. The next gap is smaller, so it does not contribute to the sequence.
The gap of 83160 between septuplets starting at p=5639 and p=88799 is the very first gap, so a(1)=88799. The gap of 195930 between septuplets starting at p=88799 and p=284729 is a maximal (record) gap - larger than any preceding gap; therefore a(2)=284729. The next gap of 341880 ending at 626609 is again a record, so a(3)=626609. The next gap is smaller, so that gap does not contribute a new term to the sequence.
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