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Search: id:A097175
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| A097175 |
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Sum k=0..n, C(floor((n+1)/2),floor((k+1)/2))4^k. |
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+0
1
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| 1, 5, 21, 105, 361, 2045, 6141, 38865, 104401, 726245, 1774821, 13394745, 30171961, 244487885, 512923341, 4424729505, 8719696801, 79515368885, 148234845621, 1420480747785, 2519992375561, 25247684340125, 42839870384541
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OFFSET
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0,2
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COMMENT
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a(n)=(5/4){1,17,17,289,289,4913...}-16{0,1,0,16,0,256...}-(1/4){1,1,1,1,1,1...}
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FORMULA
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G.f. : (1+4x-17x^2-48x^3)/((1-x)(1-16x^2)(1-17x^2)); a(n)=(5/8)((1-sqrt(17))(-sqrt(17))^n+(1+sqrt(17))(sqrt(17))^n)-2(4^n-(-4)^n)-1/4; a(n)=a(n-1)+33a(n-2)-33a(n-3)-272a(n-4)+272a(n-5).
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CROSSREFS
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Sequence in context: A017969 A050897 A046633 this_sequence A100284 A121881 A041321
Adjacent sequences: A097172 A097173 A097174 this_sequence A097176 A097177 A097178
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Jul 30 2004
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