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A051200
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Except for initial term, primes of form "n 3's followed by 1".
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14
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3, 31, 331, 3331, 33331, 333331, 3333331, 33333331, 333333333333333331, 3333333333333333333333333333333333333331, 33333333333333333333333333333333333333333333333331
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| "A remarkable pattern that is entirely accidental and leads nowhere" - M. Gardner, referring to the first 8 terms.
a(1)*a(2)*a(3) = 34179391, a Zeisel number (A051015) with coefficients (10,21).
a(1)*a(2)*a(3)*a(4) = 1139233281421, a Zeisel number with coefficients (10,21).
a(1)*a(2)*a(3)*a(4)*a(5) = 379741768929343351, a Zeisel number with coefficients (10,21).
a(1)*a(2)*a(3)*a(4)*a(5)*a(6) = 1265805010367017001532181, a Zeisel number with coefficients (10,21).
a(1)*a(2)*a(3)*a(4)*a(5)*a(6)*a(7) = 42193497392022209194699696424911, a Zeisel number with coefficients (10,21).
Primes of form (3*10^n-21)/9 (with n>1) [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 06 2010]
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REFERENCES
| M. Gardner, The Last Recreations, Springer, 1997, p. 194.
W. Sierpinski, 200 Zadan z Elementarnej Teorii Liczb, Warsaw, 1964; Problem 88 [in English: 200 Problems from the Elementary Theory of Numbers]
W. Sierpinski, 250 Problems in Elementary Number Theory. New York: American Elsevier, Warsaw, 1970, pp. 8, 56-57.
F. Smarandache, Properties of numbers, University of Craiova, 1973
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LINKS
| M. L. Perez et al., eds., Smarandache Notions Journal
Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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MATHEMATICA
| Join[{3}, Select[Rest[FromDigits/@Table[PadLeft[{1}, n, 3], {n, 50}]], PrimeQ]] (* From Harvey P. Dale, Apr 20 2011 *)
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CROSSREFS
| Cf. A055520, A089017, A089018, A093671, A056698, A105427, A105428, A033175.
Sequence in context: A011546 A152276 A136024 * A136596 A186207 A014178
Adjacent sequences: A051197 A051198 A051199 * A051201 A051202 A051203
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KEYWORD
| nonn,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| More terms from James A. Sellers (sellersj(AT)math.psu.edu)
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