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A016223
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Expansion of 1/((1-x)(1-4x)(1-7x)).
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0
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1, 12, 105, 820, 6081, 43932, 312985, 2212740, 15576561, 109385452, 767096265, 5375266260, 37649233441, 263634112572, 1845796701945, 12922008569380, 90459786608721, 633241412753292, 4432781515242025
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a(n) = (1/18)-(16/9)*4^(n-1)+(49/18)*7^(n-1) [From Antonio A Olivares (olivares14031(AT)yahoo.com), Feb 07 2010]
a(0)=1, a(1)=12, a(n)=11*a(n-1)-28*a(n-2)+1. - Vincenzo Librandi, Feb 10 2011
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EXAMPLE
| a(1); 1 a(2); 12 a(3); 105 a(4); 820 a(5); 6081 a(6); 43932 a(7); 312985 a(8); 2212740 a(9); 15576561 a(10); 109385452 [From Antonio A Olivares (olivares14031(AT)yahoo.com), Feb 07 2010]
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MAPLE
| a:=n->sum((7^(n-j)-4^(n-j))/3, j=0..n): seq(a(n), n=1..19); - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Jan 15 2007
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CROSSREFS
| Sequence in context: A157024 A051815 A004321 * A027142 A090816 A144133
Adjacent sequences: A016220 A016221 A016222 * A016224 A016225 A016226
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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