A124136 The list of primes p such that the number of primes in the open interval (p,2*p) is larger than the number of primes in the open interval (q,2*q) for all q<p.

2, 7, 11, 17, 23, 29, 31, 37, 53, 59, 71, 79, 89, 97, 101, 127, 137, 149, 157, 179, 191, 211, 223, 233, 251, 257, 263, 293, 307, 311, 331, 347, 367, 373, 379, 389, 409, 419, 431, 443, 457, 479, 487, 499, 521, 541, 547, 557, 563, 587, 599, 613, 617, 631, 641

Offset

1,1

Comments

Sequence A060715(n) lists the number of primes in the open interval (n,2*n).

If we extract its sublist for n a prime, the number of primes in the open interval (p,2*p), we have A070046(m) = 1, 1, 1, 2, 3, 3, 4, 4, 5, 6, 7, 9, 9, 9, 9, 11, 13, 12, 13, 14, 13, 15, 15, 16... for the primes p=2, 3, 5, 7, 11, 13, 17, 19 etc.

This sequence lists the primes p = prime(m) that set a new record in A070046(m).

Alternative definition: primes p defined by positions of records in A063124.

Links

Table of n, a(n) for n=1..55.

Example

a(1)=prime(1)=2 with 1 prime in the interval (2,4). a(2) is neither 3 (with 1 prime in the interval (3,6)), nor 5 (with 1 prime in the interval (5,10)), but a(2)=7 with 2 primes in the interval (7,14).
The primes 41, 43 and 47 are not in the list because the intervals (41,82), (43,86) and (47,94) contain 9 primes, but the interval (37,74) with the smaller prime p=37 already contained 9 primes.
The prime 53 is in the list because the interval (53,106) contains 11 primes and the intervals (q,2*q) for primes q =2,3, 5, ..,47 contained 9 or less primes.

Maple

ts_c:=proc(n) local i, j, st_p, max_stp, ans; ans:= [ ]: st_p:=0: max_stp:=0: for i from 2 to n do for j from i+1 to 2*i-1 do if (isprime(j) = 'true') then st_p:=st_p+1: fi od: if (st_p > max_stp and isprime(i) = 'true') then max_stp := st_p: ans:=[ op(ans), i ]: fi; st_p:=0: od: RETURN(ans) end: ts_c(1200);

Crossrefs

Cf. A060756, A060715, A084139.

Sequence in context: A168421 A038942 A175283 * A156828 A019385 A274504

Adjacent sequences: A124133 A124134 A124135 * A124137 A124138 A124139

Keyword

nonn

Author

Jani Melik, Nov 30 2006

Extensions

Definition recovered from the Maple program. - R. J. Mathar, May 21 2025

Status

approved