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A040040
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Average of twin prime pairs (A014574), divided by 2. Or, 2 a(n) +/- 1 are primes.
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31
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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; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Intersection of A005097 and A006254. - Zak Seidov (zakseidov(AT)yahoo.com), Mar 18 2005
The only possible pairs for 2a(n)+/-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 odd numbers.
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LINKS
| T. D. Noe, Table of n, a(n) for n=1..10001
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FORMULA
| a(n) = A014574(n)/2 = A054735(n+1)/4 = A111046(n+1)/8.
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MAPLE
| P := select(isprime, [$1..1789]): map(p->(p+1)/2, select(p->member(p+2, P), P)); - Peter Luschny, Mar 3 2011
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MATHEMATICA
| Select[Range[900], And @@ PrimeQ[{-1, 1} + 2# ] &] (*Chandler*)
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CROSSREFS
| Cf. A001359, A006512, A014574, A054735, A111046.
Sequence in context: A190276 A113808 * A168497 A086642 A193197 A014214
Adjacent sequences: A040037 A040038 A040039 * A040041 A040042 A040043
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KEYWORD
| nonn,easy
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from Cino Hilliard, Oct 21 2002
Title corrected by Daniel Forgues (squid(AT)zensearch.com), Jun 01 2009
Edited by Daniel Forgues (squid(AT)zensearch.com), Jun 21 2009
Comment corrected by Daniel Forgues (squid(AT)zensearch.com), Jul 12 2009
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