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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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1
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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; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| 31, 61, 181, etc. are primes.
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MATHEMATICA
| 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
| Cf. A089326.
Sequence in context: A148564 A148565 A112572 * A110593 A049368 A152733
Adjacent sequences: A089322 A089323 A089324 * A089326 A089327 A089328
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KEYWORD
| base,nonn,easy
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Nov 03 2003
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EXTENSIONS
| More terms from Ryan Propper (rpropper(AT)stanford.edu), Aug 06 2005
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