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Search: id:A040040
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| A040040 |
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Average of twin prime pairs (A014574), divided by 2. Or, 2n +/- 1 are primes. |
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+0
25
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| 2, 3, 6, 9, 15, 21, 30, 36, 51, 54, 69, 75, 90, 96, 99, 114, 120, 135, 141, 156, 174, 210, 216, 231, 261, 285, 300, 309, 321, 330, 405, 411, 414, 429, 441, 510, 516, 525, 531, 546, 576, 615, 639, 645, 651, 660, 714, 726, 741, 744, 804, 810, 834, 849, 861, 894
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Intersection of A005097 and A006254. - Zak Seidov (zakseidov(AT)yahoo.com), Mar 18 2005
The only possible pairs for 2n+/-1 are prime/prime (this sequence), not prime/not prime (A104278), prime/notprime (A104279) and not prime/prime (A104280), ... this sequence + A104280 + A104279 + A104278 = the counting numbers.
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..10001
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FORMULA
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a(n) = A014574(n)/2 = A054735(n+1)/4 = A111046(n+1)/8.
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MAPLE
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ZL:=[]:for p from 1 to 1800 do if (isprime(p) and isprime(p+2)) then ZL:=[op(ZL), (((p+2)^2)-p^2)/8]; fi; od; print(ZL); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 08 2007
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MATHEMATICA
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Select[Range[900], And @@ PrimeQ[{-1, 1} + 2# ] &] (*Chandler*)
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CROSSREFS
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Cf. A001359, A006512, A014574, A054735, A111046.
Sequence in context: A032231 A114323 A113808 this_sequence A086642 A014214 A094993
Adjacent sequences: A040037 A040038 A040039 this_sequence A040041 A040042 A040043
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KEYWORD
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nonn,easy
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AUTHOR
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njas
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EXTENSIONS
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More terms from Cino Hilliard, Oct 21 2002
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