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A063502
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a(n+1) = p, where p is the a(n)-th twin prime (p,p+2), with a(0) = 1.
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1
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OFFSET
| 0,2
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COMMENTS
| Instead of starting with a(0) = 1 for the first twin prime (3,5) other sequences can be formed for a(0) = 2, i.e. 2nd twin prime: 2, 5, 29, 641, 44381, 7212059, etc., a(0) = 4: 4, 17, 239, 12161, 1583927, etc., a(0) = 6: 6, 41, 1151, 93251, 16989317, etc., a(0) = 7: 7, 59 1931,176021, 35263691, etc., a(0) = 8: 8, 71, 2339,221201, 45749309 and so on.
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LINKS
| Tomas Oliveira e Silva, Tables of values of pi(x) and of pi2(x) [From M. F. Hasler (www.univ-ag.fr/~mhasler), Mar 02 2009]
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FORMULA
| a(n+1) = A001359(a(n)); a(0)=1. [From M. F. Hasler (www.univ-ag.fr/~mhasler), Mar 02 2009]
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EXAMPLE
| a(3) = 137 because a(2) = 11 and the 11-th twin prime is (137,139).
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MATHEMATICA
| (* Computes up to a(6) only *) tp[n_] := (* = A001359 *) tp[n] = (p = NextPrime[tp[n-1]]; While[ !PrimeQ[p+2], p = NextPrime[p]]; p); tp[1] = 3; Do[tp[n], {n, 2, 10^6}]; a[n_] := a[n] = tp[a[n-1]]; a[0]=1; Table[ Print[ a[n]]; a[n], {n, 0, 6}] (* From Jean-François Alcover, Dec 13 2011 *)
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CROSSREFS
| Cf. A007097.
Sequence in context: A057205 A121897 A067657 * A072639 A100459 A010682
Adjacent sequences: A063499 A063500 A063501 * A063503 A063504 A063505
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KEYWORD
| hard,nice,nonn
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AUTHOR
| Lubomir Alexandrov (alexandr(AT)thsun1.jinr.ru), Jul 30 2001
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EXTENSIONS
| Edited by Frank Ellermann, Jan 25, 2002
Offset and example corrected by Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 07 2008
a(7) = 65818751039 from Zak Seidov (zakseidov(AT)yahoo.com) and Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 13 2008
Computed a(8)=46091763604421 using data from T. Oliveira e Silva. M. F. Hasler (www.univ-ag.fr/~mhasler), Mar 02 2009
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