A126992 a(n) is the largest prime smaller than sqrt(prime(n)*prime(n+6)).

5, 7, 7, 13, 17, 19, 23, 23, 31, 37, 41, 47, 47, 53, 53, 61, 67, 73, 79, 83, 83, 89, 89, 97, 109, 113, 113, 113, 127, 127, 139, 139, 151, 151, 163, 163, 173, 173, 181, 181, 193, 199, 199, 199, 211, 211, 223, 233, 241, 241, 241, 251, 257, 263, 269

Offset: 1

Author

Artur Jasinski, Jan 01 2007

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Programs

Maple

f:= n -> prevprime(ceil(sqrt(ithprime(n)*ithprime(n+6)))):
map(f, [$1..100]); # Robert Israel, Jun 21 2018

Mathematica

Table[Prime[PrimePi[Sqrt[Prime[n]*Prime[n + 6]]]], {n, 1, 55}]
Table[NextPrime[Sqrt[Prime[n]Prime[n+6]],-1],{n,60}] (* Harvey P. Dale, Jul 03 2019 *)

Extensions

Edited by Stefan Steinerberger, Jul 31 2007