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3, 15, 99, 687, 4803, 33615, 235299, 1647087, 11529603, 80707215, 564950499, 3954653487, 27682574403, 193778020815, 1356446145699, 9495123019887, 66465861139203, 465261027974415, 3256827195820899, 22797790370746287
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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0,1
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LINKS
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FORMULA
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a(n) = 7*a(n-1)-6.
a(n) = 8*a(n-1)-7*a(n-2).
G.f.: 3*(1-3*x)/((1-x)*(1-7*x)).
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PROG
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(Magma) [2*7^n+1: n in [0..30]];
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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