A126991 Prime preceding the geometric mean of prime(n-2) and prime(n+2).

3, 5, 7, 11, 13, 19, 19, 23, 29, 31, 37, 43, 47, 47, 53, 61, 61, 67, 73, 79, 83, 89, 89, 97, 101, 103, 113, 113, 113, 113, 137, 139, 139, 149, 157, 157, 167, 167, 173, 181, 181, 181, 199, 199, 211, 211, 211, 229, 233, 239, 241, 241, 251, 257, 263, 271, 271, 281

Offset

3,1

Links

Table of n, a(n) for n=3..60.

Mathematica

<< NumberTheory`NumberTheoryFunctions` a = {}; Do[AppendTo[a, PreviousPrime[Sqrt[(Prime[x - 2])*(Prime[x + 2])]]], {x, 3, 100}]; a
Table[NextPrime[GeometricMean[{Prime[n-2], Prime[n+2]}], -1], {n, 3, 60}] (* Harvey P. Dale, May 14 2015 *)

Prog

(PARI) A126991(n)={ n=sqrtint(prime(n-2)*prime(n+2)); if(0==n%2, n--); while(!isprime(n), n-=2); n } /* then vector(50, n, A126991(n+2)) displays a list of values ; t=3; forprime(p=2, 999, while(A126991(t)<p, t++); if(A126991(t)>p, print(p))) prints primes 2, 17, 41, 59, ... not in this sequence */ \\ M. F. Hasler, Jun 14 2007

Crossrefs

Cf. A126990, A126992, A124662.

Sequence in context: A287441 A026603 A287437 * A264754 A130289 A071329

Adjacent sequences: A126988 A126989 A126990 * A126992 A126993 A126994

Keyword

nonn,easy,less

Author

Artur Jasinski, Jan 01 2007

Extensions

Edited by M. F. Hasler, Jun 14 2007

Status

approved