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Search: id:A115099
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| A115099 |
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a(0)=4, a(n)=3*a(n-1)-4. |
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+0
1
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| 4, 8, 20, 56, 164, 488, 1460, 4376, 13124, 39368, 118100, 354296, 1062884, 3188648, 9565940, 28697816, 86093444, 258280328, 774840980, 2324522936, 6973568804, 20920706408, 62762119220, 188286357656, 564859072964, 1694577218888
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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A tetrahedron has 4 faces. Let's cut every corner so that we get triangular faces. This polyhedron has 8 faces. This procedure gives 4,8,20,56... faced polyhedra.
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FORMULA
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a(n)=2*3^n+2
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EXAMPLE
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a(4)=164=2*3^4+2=2*81+2=3*a(3)-4=3*56-4
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MAPLE
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seq(2*3^i+2, i=0..30);
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CROSSREFS
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Sequence in context: A084219 A009916 A123861 this_sequence A060919 A009333 A086912
Adjacent sequences: A115096 A115097 A115098 this_sequence A115100 A115101 A115102
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KEYWORD
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easy,nonn
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AUTHOR
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Miklos Kristof (kristmikl(AT)freemail.hu), Mar 02 2006
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