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Search: id:A144927
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| A144927 |
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Numbers n such that there exists an integer k with (n+1)^3-n^3=k^2. |
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+0
4
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| 7, 1162, 128191, 14100226, 1550897047, 170584575322, 18762752388751, 2063732178187666, 226991776848254887, 24967031721129850282
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Numbers x such that there exists an integer n with (x+7)^3-x^3=n^2. Richard Choulet (richardchoulet(AT)yahoo.fr), Oct 16 2008
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FORMULA
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a(n+2)=110*a(n+1)-a(n)+378
a(n)=-(7/2)+(21/4)*{[55+12*sqrt(21)]^n+[55-12*sqrt(21))^n}+(7/6)*sqrt(21)*{[55+12*sqrt(21)]^n-[55-12*sqrt(21)]^n}, with n>=0 [From Paolo P. Lava (ppl(AT)spl.at), Nov 25 2008]
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EXAMPLE
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a(1)=7 because 14^3-7^3=49^2
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CROSSREFS
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Cf. A144928.
A144928, A144930, A144929 [From Richard Choulet (richardchoulet(AT)yahoo.fr), Oct 16 2008]
Sequence in context: A004807 A139781 A101072 this_sequence A159994 A119181 A152518
Adjacent sequences: A144924 A144925 A144926 this_sequence A144928 A144929 A144930
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KEYWORD
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easy,nonn
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AUTHOR
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Richard Choulet (richardchoulet(AT)yahoo.fr), Sep 25 2008
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