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A145025
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Numbers which are the average of two consecutive odd primes (A024675) together with primes which are the average of the previous prime and the following prime (A006562).
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9
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4, 5, 6, 9, 12, 15, 18, 21, 26, 30, 34, 39, 42, 45, 50, 53, 56, 60, 64, 69, 72, 76, 81, 86, 93, 99, 102, 105, 108, 111, 120, 129, 134, 138, 144, 150, 154, 157, 160, 165, 170, 173, 176, 180, 186, 192, 195, 198, 205, 211, 217, 225, 228, 231, 236, 240, 246, 254, 257, 260
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OFFSET
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1,1
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COMMENTS
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Numbers n such that prevprime(n) + nextprime(n) = 2n. - Wesley Ivan Hurt, May 13 2017
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LINKS
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MAPLE
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Primes:= select(isprime, [seq(i, i=3..1000, 2)]):
nprimes:= nops(Primes):
A024675:= {seq((Primes[i]+Primes[i+1])/2, i=1..nprimes-1)}:
L:= Primes[1..-3]+Primes[3..-1]:
A006562:=zip((s, t) -> if 2*s=t then s else NULL fi, Primes[2..-2], L):
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MATHEMATICA
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Union[Select[Map[Mean@ {First@ #, Last@ #} &, Partition[#, 3, 1]], PrimeQ], Map[Mean, Partition[#, 2, 1]]] &@ Prime@ Range[2, 56] (* Michael De Vlieger, Jan 31 2019 *)
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PROG
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(PARI) for(n=2, 999, n-precprime(n-1)==nextprime(n+1)-n&&print1(n", ")) \\ M. F. Hasler, Jun 01 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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