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A024675
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Average of two consecutive odd primes.
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98
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4, 6, 9, 12, 15, 18, 21, 26, 30, 34, 39, 42, 45, 50, 56, 60, 64, 69, 72, 76, 81, 86, 93, 99, 102, 105, 108, 111, 120, 129, 134, 138, 144, 150, 154, 160, 165, 170, 176, 180, 186, 192, 195, 198, 205, 217, 225, 228, 231, 236, 240, 246, 254, 260, 266, 270, 274, 279, 282, 288, 300
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listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Sometimes called interprimes.
Never prime, for that would contradict the definition. - Jon Perry, Dec 05 2012
A subset of A145025, obtained from that sequence by omitting the primes (which are barycenter of their neighboring primes). - M. F. Hasler, Jun 01 2013
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LINKS
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FORMULA
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Conjecture: a(n) = ceiling(sqrt(prime(n+1)*prime(n+2))). - Thomas Ordowski, Mar 22 2013 [This requires gaps to be smaller than approximately sqrt(8p) and hence requires a result on prime gaps slightly stronger than that provided by the Riemann hypothesis. - Charles R Greathouse IV, Jul 13 2022]
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MAPLE
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seq( ( (ithprime(x)+ithprime(x+1))/2 ), x=2..40);
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MATHEMATICA
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Plus @@@ Partition[Table[Prime[n], {n, 2, 100}], 2, 1]/2
Mean/@Partition[Prime[Range[2, 70]], 2, 1] (* Harvey P. Dale, Jul 28 2020 *)
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PROG
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(PARI) for(X=2, 50, print((prime(X)+prime(X+1))/2)) \\ Hauke Worpel (thebigh(AT)outgun.com), May 08 2008
(Python)
from sympy import prime
def a(n): return (prime(n + 1) + prime(n + 2)) // 2
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CROSSREFS
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KEYWORD
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nonn,nice,easy
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AUTHOR
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STATUS
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approved
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