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Search: id:A089325
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| A089325 |
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a(1) = 3, a(n) = smallest multiple of a(n-1) such that 10*a(n) + 1 is prime. |
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2
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| 3, 6, 18, 54, 162, 486, 972, 1944, 5832, 40824, 204120, 408240, 816480, 1632960, 3265920, 6531840, 26127360, 130636800, 391910400, 1175731200, 14108774400, 56435097600, 1241572147200, 8691005030400, 26073015091200, 260730150912000
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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31, 61, 181, etc. are primes.
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MATHEMATICA
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k = 3; Print[k]; Do[i = 2; While[ !PrimeQ[10*i*k + 1], i++ ]; k *= i; Print[k], {n, 1, 30}] (Propper)
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CROSSREFS
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Cf. A089326.
Sequence in context: A148564 A148565 A112572 this_sequence A110593 A049368 A152733
Adjacent sequences: A089322 A089323 A089324 this_sequence A089326 A089327 A089328
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KEYWORD
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base,nonn,easy
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 03 2003
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EXTENSIONS
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More terms from Ryan Propper (rpropper(AT)stanford.edu), Aug 06 2005
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