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A083969
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Numbers n such that 2.n.3.n.5.n.7.n.11 is prime (dot means concatenation).
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4
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4, 18, 33, 42, 43, 57, 73, 76, 78, 87, 91, 93, 97, 102, 112, 114, 120, 141, 151, 177, 186, 193, 196, 219, 261, 267, 276, 280, 300, 307, 318, 322, 342, 352, 364, 366, 402, 435, 438, 445, 457, 462, 468, 484, 511, 580, 582, 633, 646, 651, 679, 706, 745, 774, 783
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| 2.4.3.4.5.4.7.4.11 = 2434547411, which is prime. Hence 4 is in the sequence.
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MATHEMATICA
| v={}; Do[If[PrimeQ[FromDigits[Join[{2}, IntegerDigits[n], {3}, IntegerDigits[n], {5}, IntegerDigits[n], {7}, IntegerDigits[n], {1, 1}]]], v=Append[v, n]], {n, 1000}]; v
Select[Range[660], PrimeQ[FromDigits[Join[{2}, IntegerDigits[ # ], {3}, IntegerDigits[ # ], {5}, IntegerDigits[ # ], {7}, IntegerDigits[ # ], {1, 1}]]] &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 28 2007
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CROSSREFS
| Cf. A083677, A032711, A092115, A092117.
Sequence in context: A003474 A095823 A092116 * A110621 A124978 A031081
Adjacent sequences: A083966 A083967 A083968 * A083970 A083971 A083972
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KEYWORD
| base,easy,nonn
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AUTHOR
| Farideh Firoozbakht (f.firoozbakht(AT)sci.ui.ac.ir), Jun 19 2003
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EXTENSIONS
| Edited by Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 28 2007
Edited by N. J. A. Sloane (njas(AT)research.att.com), Sep 18 2008 at the suggestion of R. J. Mathar.
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