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Search: id:A131760
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| A131760 |
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Numbers n such that n multiplied by its reverse yields a fourth power. |
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+0
1
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| 1, 4, 9, 121, 484, 676, 2178, 8712, 10000, 10201, 12321, 14641, 40000, 40804, 44944, 69696, 90000, 94249, 698896, 1002001, 1210000, 1234321, 4008004, 4840000, 5221225, 6760000, 6948496, 21780000, 87120000, 100000000, 100020001
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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This sequence contains palindromic squares and palindromic squares with trailing zeros. Are 2178 and 8721 the only non-palindromic reversible pair in this sequence without trailing zeros?
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EXAMPLE
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2178 = 2*9*121 and 8712 = 8*9*121, 2718*8712 = (2*3*11)^4.
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MATHEMATICA
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Select[Range[1000000], IntegerQ[(#*FromDigits[Reverse[IntegerDigits[ # ]]])^(1/4)] &]
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CROSSREFS
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Cf. A002779 = Palindromic squares.
Sequence in context: A115676 A115667 A158642 this_sequence A002779 A028817 A057136
Adjacent sequences: A131757 A131758 A131759 this_sequence A131761 A131762 A131763
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KEYWORD
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nonn,base
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AUTHOR
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Tanya Khovanova (tanyakh(AT)yahoo.com), Sep 17 2007
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EXTENSIONS
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a(20)-a(31) from Donovan Johnson (donovan.johnson(AT)yahoo.com), Oct 27 2008
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