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A256753
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Numbers n such that n is both the average of some twin prime pair p, q (q = p+2) (i.e., n = p+1 = q-1) and is also the average of the prime before p and the prime after q.
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18
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12, 18, 30, 42, 60, 102, 108, 228, 270, 312, 420, 462, 570, 600, 858, 882, 1050, 1092, 1230, 1290, 1302, 1428, 1488, 1620, 1872, 1998, 2028, 2340, 2550, 2688, 2730, 3390, 3462, 3540, 3582, 4020, 4230, 4242, 4272, 4338, 4518, 4650, 4788
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OFFSET
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1,1
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COMMENTS
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This sequence is a subsequence of A014574 (average of twin prime pairs).
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LINKS
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EXAMPLE
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For n=12: 7, 11, 13, 17 are four consecutive primes with 13 = 11 + 2 and (7+17)/2 = 12.
For n=18: 13, 17, 19, 23 are four consecutive primes with 19 = 17 + 2 and (13+23)/2 = 18.
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MATHEMATICA
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Select[Prime[Range[10^3]], PrimeQ[#+2]&&2*#+2==NextPrime[#, -1]+NextPrime[#, 2]&]+1 (* Ivan N. Ianakiev, Apr 23 2015 *)
Select[Partition[Prime[Range[700]], 4, 1], #[[3]]-#[[2]]==2&&(#[[1]]+#[[4]])/2 == (#[[2]]+#[[3]])/2&][[All, 2]]+1 (* Harvey P. Dale, May 06 2022 *)
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PROG
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(Python)
from sympy import isprime, prevprime, nextprime
for i in range(5, 12001, 2):
..if isprime(i) and isprime(i+2):
....if prevprime(i)+nextprime(i, 2) == 2*(i+1): print(i+1, end=', ')
(PARI) lista(nn) = {forprime(p=3, nn, if (isprime(p+2), if (precprime(p-1)+nextprime(p+3) == 2*(p+1), print1(p+1, ", ")); ); ); } \\ Michel Marcus, Apr 12 2015
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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