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Search: id:A030485
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| A030485 |
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Squares composed of digits {2,5,7}. |
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+0
3
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| 25, 225, 7225, 27225, 55225, 2772225, 227557225, 277722225, 27777222225, 72272257225, 2777772222225, 25772527522225, 277777722222225, 2775552752755225, 27522257555772225, 27777777222222225, 77525222275255225
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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We can easily prove that except for the first term all terms are of the form 100*m^2+100*m+25 where mod(m, 10) is one of the numbers 1, 3, 6 & 8. Also we can show that all numbers of the form ((5*10^n-5)/3)^2 where n is a natural number, are in the sequence. [From Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 09 2008]
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LINKS
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P. De Geest, Squares containing at most three distinct digits, Index entries for related sequences
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CROSSREFS
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Cf. A030487.
Sequence in context: A067472 A058426 A048384 this_sequence A036509 A034981 A053919
Adjacent sequences: A030482 A030483 A030484 this_sequence A030486 A030487 A030488
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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)
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EXTENSIONS
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Extended and corrected by author 03/2000.
a(17)-a(19) from Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 09 2008
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