A370517 a(n) is the largest prime p such that all prime numbers q <= p have distinct length n prime gap sequences.

3, 7, 7, 7, 47, 251, 421, 421, 9769, 9769, 36469, 36469, 36469, 184224493, 2159263321, 13848073963, 33980350373

Offset

1,1

Comments

Given p(i) the i-th prime number, the gap sequence of length n for prime p(i) is defined as: p(i+1)-p(i), p(i+2)-p(i+1), ..., p(i+n)-p(i+n-1). E.g., the length 3 gap sequence of 7 is [11-7, 13-11, 17-13] is [4, 2, 4].

Links

Table of n, a(n) for n=1..17.

Example

For n = 5, the largest prime with a distinct gap sequence is 47. For all primes up to and including 47, the length 5 gap sequences are distinct, while the next prime, 53, has a gap sequence equal to 23, namely [6, 2, 6, 4, 2].

Prog

(Python)
s = set()
for p, g in ((w[0][0], tuple(r - q for q, r in w[1:])) for w in sliding_window(pairwise(primes()), n + 1)):
    if g in s: return p
    else: s.add(g)

Crossrefs

Cf. A001223.

Sequence in context: A193016 A349604 A325894 * A176269 A343644 A081522

Adjacent sequences: A370513 A370514 A370516 * A370518 A370519 A370520

Keyword

nonn,more

Author

Leo Vandriel, Feb 21 2024

Status

approved