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Search: id:A126991
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| A126991 |
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Prime preceding the geometric mean of prime(n-2) and prime(n+2). |
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+0
1
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| 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
(list; graph; listen)
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OFFSET
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3,1
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MATHEMATICA
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<< NumberTheory`NumberTheoryFunctions` a = {}; Do[AppendTo[a, PreviousPrime[Sqrt[(Prime[x - 2])*(Prime[x + 2])]]], {x, 3, 100}]; a
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PROGRAM
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(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
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CROSSREFS
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Cf. A126990, A126992, A124662.
Sequence in context: A130122 A046494 A026603 this_sequence A130289 A132779 A071329
Adjacent sequences: A126988 A126989 A126990 this_sequence A126992 A126993 A126994
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KEYWORD
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nonn,easy,less
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AUTHOR
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Artur Jasinski (grafix(AT)csl.pl), Jan 01 2007
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EXTENSIONS
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Edited by M. F. Hasler (Maximilian.Hasler(AT)gmail.com), Jun 14 2007
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