A052359 Least prime in A031938 (lesser of primes differing by 20) whose distance to the next 20-twin is 6*n.

46703, 37223, 65147, 20369, 63929, 71999, 11597, 11027, 99767, 93503, 5903, 14087, 115163, 24821, 104891, 24923, 11867, 53381, 65657, 93581, 99623, 11447, 18461, 126761, 32213, 27653, 72797, 5717, 154247, 54449, 27827, 10223, 56747, 18617, 13421, 10433, 8543, 60107

Offset

4,1

Comments

The smallest distance between 20-twins is 24 [= A052380(10)], while its minimal increment is 6.

a(n) = p starts [p, p+20, p+6n, p+6n+20] and [20, 6n-20, 20] patterns of primes and their difference.

a(n) = p is the smallest prime which starts a [p, p+20] twin followed by the next [p+6n, p+6n+20] twin.

Links

Amiram Eldar, Table of n, a(n) for n = 4..1003

Example

For n = 4, a(4) = 46703 results in prime quadruple [46703, 46723, 46727, 46747] and difference pattern [20, 4, 20].
For n = 14, a(14) = 5903 yields prime quadruple [5903, 5923, 5987, 6007] with 4 primes in the medial gap, and difference pattern [20, 64, 20].

Mathematica

seq[m_] := Module[{p = Prime[Range[m]], d, i, pp, dd, j}, d = Differences[p]; i = Position[d, 20] // Flatten; pp = p[[i]]; dd = Differences[pp]/6 - 3; j = TakeWhile[FirstPosition[dd, #] & /@ Range[Max[dd]] // Flatten, ! MissingQ[#] &]; pp[[j]]]; seq[15000] (* Amiram Eldar, Mar 05 2025 *)

Prog

(PARI) list(len) = {my(s = vector(len), c = 0, p1 = 2, q1 = 0, q2, d); forprime(p2 = 3, , if(p2 == p1 + 20, q2 = p1; if(q1 > 0, d = (q2 - q1)/6 - 3; if(d <= len && s[d] == 0, c++; s[d] = q1; if(c == len, return(s)))); q1 = q2); p1 = p2); } \\ Amiram Eldar, Mar 05 2025

Crossrefs

Cf. A031938, A052380, A052381, A053331.

Cf. A052350, A052351, A052352, A052353, A052354, A052355, A052356, A052357, A052358.

Sequence in context: A265285 A255514 A251502 * A205752 A205474 A232411

Adjacent sequences: A052356 A052357 A052358 * A052360 A052361 A052362

Keyword

nonn,changed

Author

Labos Elemer, Mar 07 2000

Extensions

Offset changed to 1 by Michel Marcus, Apr 30 2019

Name and offset corrected by Amiram Eldar, Mar 05 2025

Status

approved