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A103897
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3*2^(n-1)*(2^n-1).
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2
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3, 18, 84, 360, 1488, 6048, 24384, 97920, 392448, 1571328, 6288384, 25159680, 100651008, 402628608, 1610563584, 6442352640, 25769607168, 103078821888, 412316073984, 1649265868800, 6597066620928, 26388272775168, 105553103683584, 422212439900160
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Divide the sequence of natural numbers: s0=1,2,3,4,5,6,7,8,9,10,11,12,13,14,... into sections s(n) of length 2*s1-1, where s1=initial digits of s(n): s={1,2},{3,4,5,6},{7,8,9,10,11,12,13,14},... then a(n)=sum of terms of s(n):3,18,84,...
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LINKS
| Vincenzo Librandi, Table of n, a(n) for n = 1..1000
Index to sequences with linear recurrences with constant coefficients, signature (6,-8).
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FORMULA
| a(n) = 3*A006516(n).
G.f.: 3*x/((1-2*x)*(1-4*x)). a(n+2) = A061561(4n-2). - Bruno Berselli, Sep 19 2011
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MATHEMATICA
| Table[3*2^(n - 1)*(2^n - 1), {n, 30}]
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PROG
| (MAGMA) [3*2^(n-1)*(2^n-1): n in [1..24]]; // Bruno Berselli, Sep 19 2011
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CROSSREFS
| Cf. A006516.
Sequence in context: A078904 A099012 A122069 * A119424 A037295 A124811
Adjacent sequences: A103894 A103895 A103896 * A103898 A103899 A103900
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KEYWORD
| nonn,easy
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AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Mar 30 2005
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EXTENSIONS
| More terms by Bruno Berselli, Sep 19 2011
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