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Search: id:A054216
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| A054216 |
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Numbers n such that n^2 is a concatenation of two consecutive decreasing numbers. |
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+0
8
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| 91, 9079, 9901, 733674, 999001, 88225295, 99990001, 8900869208, 9296908812, 9604060397, 9999900001, 326666333267, 673333666734, 700730927008, 972603739727, 999999000001, 34519562953737, 39737862788838, 49917309624956
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Obviously, b(n) = 100^n-10^n+1 = (91,9901,999001,99990001,...) is a subsequence. Are { b(2), b(4), b(6), b(8) } the only terms of this sequence which are prime? - Maximilian F. Hasler (www.univ-ag.fr/~mhasler), Mar 30 2008
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FORMULA
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a(n) = sqrt(A054215(n)). - Max Alexseyev, May 14 2007
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EXAMPLE
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E.g. '8242' + '8242-1' gives 82428241 which is 9079^2.
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CROSSREFS
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Cf. A054214, A054215, A030465, A030466, A030467, A020339, A020340.
Cf. A054214, A054215, A030465, A030466, A030467, A020339, A020340.
Adjacent sequences: A054213 A054214 A054215 this_sequence A054217 A054218 A054219
Sequence in context: A022253 A060078 A006244 this_sequence A109627 A095372 A015261
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KEYWORD
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nonn,base
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AUTHOR
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Patrick De Geest (pdg(AT)worldofnumbers.com), Feb 15 2000.
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EXTENSIONS
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More terms from Max Alexseyev, May 14 2007
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