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A101180
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Numbers n such that 19*n^2 + 19*n + 1 is a square.
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1
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0, 8, 671, 15639, 42159, 981911, 77624048, 1807894920, 4873553880, 113507005568, 8973184757831, 208989037004319, 563373081435879, 13121182828725551, 1037282211558181688, 24158714697817430640, 65124801462951244560
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| Define a(1)=0, a(2)=8, a(3)=671, a(4)=15639, a(5)=42159, a(6)=981911, the first 6 terms found for the sequence then a(7)=57799*(2*a(3)+1)-a(2)-1, a(8)=57799*(2*a(4)+1)-a(1)-1 for n>8 a(n)=57799*(2*a(n-4)+1)-a(n-8)-1 remark:57799 = 38*39*39+1 =2*19*(39^2)+1
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CROSSREFS
| Cf. A105839.
Sequence in context: A015106 A099126 A172919 * A128875 A199801 A202910
Adjacent sequences: A101177 A101178 A101179 * A101181 A101182 A101183
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KEYWORD
| nonn
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AUTHOR
| Pierre CAMI (pierre-cami(AT)bbox.fr), Apr 06 2005, Apr 22 2005
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), Aug 29 2008 at the suggestion of R. J. Mathar
More terms (using recursive formula in comment) from Jon E. Schoenfield (jonscho(AT)hiwaay.net), Jul 10 2010
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