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Search: id:A055793
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| A055793 |
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Numbers n such that n and floor[n/3] are both squares; i.e. squares which remain squares when written in base 3 and last digit is removed. |
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+0
5
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| 0, 1, 4, 49, 676, 9409, 131044, 1825201, 25421764, 354079489, 4931691076, 68689595569, 956722646884, 13325427460801, 185599261804324
(list; graph; listen)
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OFFSET
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1,3
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COMMENT
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Or, squares of the form 3n^2+1.
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FORMULA
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Conjecture: a(n)=3*A098301(n-2)+1. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jun 11 2009]
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EXAMPLE
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a(3) = 49 because 49 = 7^2 = 1211 base 3 and 121 base 3 = 16 = 4^2
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PROGRAM
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(PARI) sq3nsqplus1(n) = { for(x=1, n, y = 3*x*x+1; \ print1(y" ") if(issquare(y), print1(y" ")) ) }
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CROSSREFS
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Cf. A023110.
Sequence in context: A067474 A053769 A086094 this_sequence A144656 A121275 A029991
Adjacent sequences: A055790 A055791 A055792 this_sequence A055794 A055795 A055796
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KEYWORD
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base,nonn
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AUTHOR
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Henry Bottomley (se16(AT)btinternet.com), Jul 14 2000
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EXTENSIONS
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More terms from Cino Hilliard (hillcino368(AT)gmail.com), Mar 01 2003
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