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0, 4, 32, 192, 1024, 5120, 24576, 114688, 524288, 2359296, 10485760, 46137344, 201326592, 872415232, 3758096384, 16106127360, 68719476736, 292057776128, 1236950581248, 5222680231936, 21990232555520
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Bisection of A001787. That is, a(n)=A001787(2*n) - Graeme McRae (g_m(AT)mcraefamily.com), Jul 12 2006
All numbers of the form n*4^n+(4^n-1)/3 have the property that they are sums of two squares and also their indices are the sum of two squares. This follows from the identity n*4^n+(4^n-1)/3=4*(4*(..4*(4*n+1)+1)+1)+1..)+1. - Artur Jasinski (grafix(AT)csl.pl), Nov 12 2007
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 0..300
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FORMULA
| G.f.: 4*x/(1-4*x)^2.
E.g.f.: 4*x*exp(4*x).
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PROG
| (MAGMA) [n*4^n: n in [0..25]]; // Vincenzo Librandi, Jun 01 2011
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CROSSREFS
| Cf. A002450.
Sequence in context: A123854 A113154 A083299 * A099133 A043018 A002012
Adjacent sequences: A018212 A018213 A018214 * A018216 A018217 A018218
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Peter Winkler (pw(AT)bell-labs.com)
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