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Search: id:A133197
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| A133197 |
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Triangular numbers such that moving the first digit to the end produces a square number. |
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+0
1
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| 1, 10, 136, 406, 111628, 400960, 624403, 40423536, 1119043156276, 4291092052416, 600441627703203
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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The square roots are: 1, 1, 19, 8, 341, 98, 494, 2058, 1091069, 1706142, 2101494 - Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2007
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EXAMPLE
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136 is a triangular number, 361 is a square number - hence 136 belongs to this sequence.
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MATHEMATICA
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Select[Table[n(n + 1)/2, {n, 1000000}], IntegerQ[Sqrt[ FromDigits[ Append[Drop[IntegerDigits[ # ], 1], First[IntegerDigits[ # ]]]]]] &]
lst = {}; Do[ t = n (n + 1)/2; id = IntegerDigits@ t; If[MemberQ[{1, 4, 5, 6, 9}, id[[1]]] && IntegerQ@ Sqrt@ FromDigits@ RotateLeft@ id, AppendTo[lst, t]; Print@t], {n, 44000000}]; lst - Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2007
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CROSSREFS
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Sequence in context: A095653 A024135 A050408 this_sequence A128862 A129803 A065024
Adjacent sequences: A133194 A133195 A133196 this_sequence A133198 A133199 A133200
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KEYWORD
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base,nonn
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AUTHOR
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Tanya Khovanova (tanyakh(AT)yahoo.com), Oct 09 2007
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EXTENSIONS
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More terms from Robert G. Wilson v (rgwv(AT)rgwv.com), Oct 14 2007
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