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A054416
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Numbers n such that 9090...9091 (with n-1 copies of 90 and one copy of 91) is prime.
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3
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OFFSET
| 1,1
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REFERENCES
| J. A. H. Hunter and J. S. Madachy, Mathematical Diversions, New York: Dover Publications, Inc., 1974, pp. 4-5. Originally published by Van Nostrand, 1963.
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LINKS
| D. Broadhurst, Proof that 1505 term is prime
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FORMULA
| 10*(10^(2n)-1)/11 + 1 is prime.
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EXAMPLE
| The first 3 numbers are 9091, 909091, 909090909090909091
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MATHEMATICA
| Do[ If[ PrimeQ[ 10*(10^(2n) - 1)/11 + 1], Print[ n ] ], {n, 0, 1505} ]
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CROSSREFS
| Equals (A001562-1)/2.
Sequence in context: A092352 A061933 A124881 * A092638 A206777 A173809
Adjacent sequences: A054413 A054414 A054415 * A054417 A054418 A054419
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KEYWORD
| nonn
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AUTHOR
| Antreas P. Hatzipolakis (xpolakis(AT)otenet.gr), May 22 2000
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EXTENSIONS
| More terms from Michael Kleber (michael.kleber(AT)gmail.com) and Harvey Dubner (harvey(AT)dubner.com), May 22, 2000
Ignacio Larrosa Canestro (ignacio.larrosa(AT)eresmas.net) reports that the 1068 term has now been established to be a prime using Titanix 1.01, Oct 23 2000
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