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3, 5, 7, 11, 13, 17, 19, 29, 31, 41, 43, 59, 61, 71, 73, 101, 103, 107, 109, 137, 139, 149, 151, 179, 181, 191, 193, 197, 199, 227, 229, 239, 241, 269, 271, 281, 283, 311, 313, 347, 349, 419, 421, 431, 433, 461, 463, 521, 523, 569, 571, 599, 601, 617, 619, 641, 643
(list;
graph;
refs;
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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Union of A001359 and A006512.
The only twin primes that are Fibonacci numbers are 3, 5 and 13 [MacKinnon]. - Emeric Deutsch, Apr 24 2005
(p, p+2) are twin primes if and only if p + 2 can be represented as the sum of two primes. Brun (1919): Even if there are infinitely many twin primes, the series of all twin prime reciprocals does converges to [Brun's constant] (A065421). Clement (1949): For every n > 1, (n, n+2) are twin primes if and only if 4((n-1)! + 1) == -n (mod n(n+2)). - Stefan Steinerberger, Dec 04 2005
A164292(a(n)) = 1. - Reinhard Zumkeller, Mar 29 2010
The 100355-digit numbers, 65516468355 · 2^333333 +/- 1, are currently the largest known twin primes. They were discovered by Twin Prime Search and Primegrid in August 2009. - Paul Muljadi, Mar 07 2011
For every n > 2, the pair (n, n+2) is a twin prime if and only if ((n-1)!!)^4 == 1 (mod n*(n+2)). - Thomas Ordowski, Aug 15 2016
For every n > 1, the pair (n, n+2) is a twin prime if and only if (4*n!+n*(n+4)) == 0 (mod n^2*(n+2)). - Davide Rotondo, Sep 08 2020
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REFERENCES
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P. Ribenboim, The New Book of Prime Number Records, Springer-Verlag, p. 259-265.
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LINKS
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T. D. Noe, Table of n, a(n) for n = 1..10000
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972, p. 870.
J. P. Delahaye, Premiers jumeaux: frères ennemis? [Twin primes: Enemy Brothers?], Pour la science, No. 260 (Juin 1999), 102-106.
Harvey Dubner, Twin Prime Statistics, Journal of Integer Sequences, Vol. 8 (2005), Article 05.4.2.
J. C. Evard, Twin primes and their applications [Cached copy on the Wayback Machine]
J. C. Evard, Twin primes and their applications [Local cached copy]
J. C. Evard, Twin primes and their applications [Pdf file of cached copy]
Andrew Granville, Primes in intervals of bounded length, Joint Math Meeting, Current Events Bulletin, Baltimore, Friday, Jan 17 2014.
N. MacKinnon, Problem 10844, Amer. Math. Monthly 109, (2002), p. 78.
James Maynard, Small gaps between primes, arXiv:1311.4600 [math.NT], 2013, Annals of Mathematics, to appear.
Omar E. Pol, Determinacion geometrica de los numeros primos y perfectos.
D. H. J. Polymath, New equidistribution estimates of Zhang type, and bounded gaps between primes, arXiv:1402.0811 [math.NT], 2014.
D. H. J. Polymath, Variants of the Selberg sieve, and bounded intervals containing many primes, arXiv:1407.4897 [math.NT], 2014.
Eric Weisstein's World of Mathematics, Twin Primes
Yitang Zhang, Bounded gaps between primes, Annals of Mathematics, Pages 1121-1174, Volume 179 (2014), Issue 3.
Index entries for primes, gaps between
Index entries for "core" sequences
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MAPLE
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A001097 := proc(n)
option remember;
if n = 1 then
3;
else
for a from procname(n-1)+1 do
if isprime(a) and ( isprime(a-2) or isprime(a+2) ) then
return a;
end if;
end do:
end if;
end proc: # R. J. Mathar, Feb 19 2015
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MATHEMATICA
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Select[ Prime[ Range[120]], PrimeQ[ # - 2] || PrimeQ[ # + 2] &] (* Robert G. Wilson v, Jun 09 2005 *)
Union[Flatten[Select[Partition[Prime[Range[200]], 2, 1], #[[2]]-#[[1]] == 2&]]] (* Harvey P. Dale, Aug 19 2015 *)
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PROG
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(PARI) isA001097(n) = (isprime(n) && (isprime(n+2) || isprime(n-2))) \\ Michael B. Porter, Oct 29 2009
(PARI) a(n)=if(n==1, return(3)); my(p); forprime(q=3, default(primelimit), if(q-p==2 && (n-=2)<0, return(if(n==-1, q, p))); p=q) \\ Charles R Greathouse IV, Aug 22 2012
(PARI) list(lim)=my(v=List([3]), p=5); forprime(q=7, lim, if(q-p==2, listput(v, p); listput(v, q)); p=q); if(p+2>lim && isprime(p+2), listput(v, p)); Vec(v) \\ Charles R Greathouse IV, Mar 17 2017
(Haskell)
a001097 n = a001097_list !! (n-1)
a001097_list = filter ((== 1) . a164292) [1..]
-- Reinhard Zumkeller, Feb 03 2014, Nov 27 2011
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CROSSREFS
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Cf. A070076, A001359, A006512, A164292. See A077800 for another version.
Sequence in context: A045393 A132143 A239879 * A117243 A179679 A059362
Adjacent sequences: A001094 A001095 A001096 * A001098 A001099 A001100
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KEYWORD
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nonn,core,nice
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AUTHOR
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N. J. A. Sloane, Mar 15 1996
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STATUS
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approved
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