A368549 a(n) is the least k such that the greatest prime less than n*k is less than n times the greatest prime < k.

8, 12, 24, 24, 20, 18, 38, 14, 54, 30, 138, 98, 152, 90, 84, 80, 240, 504, 68, 200, 354, 854, 224, 1020, 230, 180, 510, 542, 524, 522, 368, 968, 578, 1098, 1130, 3462, 744, 504, 1218, 1988, 468, 938, 812, 758, 684, 4002, 2592, 642, 3120, 4458, 2958, 3272, 4920, 572, 5060, 3300, 14490, 3188, 6012

Offset

2,1

Comments

a(n) = p + 1 where p is the first prime such that there are no primes between n*p and n*(p+1).

Links

Robert Israel, Table of n, a(n) for n = 2..280

Example

a(4) = 24 because the greatest prime < 24 is 23 and the greatest prime < 4*24 is 89 < 4*23.

Maple

f:= proc(n) local p;
   p:= 1;
   do
     p:= nextprime(p);
     if not ormap(isprime, [$ (n*p+1) .. (n*p+n-1)]) then return p+1 fi
   od
end proc:
map(f, [$2..100]);

Crossrefs

Cf. A367035.

Sequence in context: A105571 A350633 A141616 * A326994 A367146 A278902

Adjacent sequences: A368546 A368547 A368548 * A368550 A368551 A368552

Keyword

nonn

Author

Robert Israel, Dec 29 2023

Status

approved