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A098855
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Numbers n such that (2^n)*(2^n + 1) - 1 is prime.
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1
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1, 2, 3, 4, 6, 10, 16, 24, 26, 35, 52, 55, 95, 144, 379, 484, 939, 1284, 1300, 2651, 3644, 3979, 7179, 8304
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Or, numbers n such that 4^n+2^n-1 is prime.
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FORMULA
| A110082(n)=2^(a(n)-1)*(4^a(n)+2^a(n)-1).
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EXAMPLE
| 1300 is in the sequence because 4^1300+2^1300-1 is prime.
(2^1)*(2^1 + 1)-1 = 5
(2^2)*(2^2 + 1)-1 = 19
(2^3)*(2^3 + 1)-1 = 71
(2^4)*(2^4 + 1)-1 = 271
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MATHEMATICA
| Do[If[PrimeQ[4^m+2^m-1], Print[m]], {m, 8000}] - Farideh Firoozbakht (mymontain(AT)yahoo.com), Aug 03 2005
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CROSSREFS
| Cf. A110079, A110082.
Sequence in context: A186426 A018062 A070542 * A143283 A104767 A072944
Adjacent sequences: A098852 A098853 A098854 * A098856 A098857 A098858
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KEYWORD
| nonn
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AUTHOR
| Pierre CAMI (pierre-cami(AT)bbox.fr), Oct 11 2004
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EXTENSIONS
| Corrected by Torin Huzil (thuzil(AT)gmail.com), Sep 15 2005
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