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Search: id:A081186
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| 1, 4, 17, 76, 353, 1684, 8177, 40156, 198593, 986404, 4912337, 24502636, 122336033, 611148724, 3054149297, 15265963516, 76315468673, 381534296644, 1907542343057, 9537324294796, 47685459212513, 238423809278164
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OFFSET
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0,2
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COMMENT
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Binomial transform of A007582.
a(n) is a companion to A005059(n): a(n) + A005059(n) = 5^n; e.g. a(4) = A005059(4) = 353 + 272 = 625 = 5^4. - Gary W. Adamson (qntmpkt(AT)yahoo.com), Jun 30 2006
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FORMULA
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a(n)=8a(n-1)-15a(n-2), a(0)=1, a(1)=4. G.f.: (1-4x)/((1-3x)(1-5x)). a(n)=3^n/2+5^n/2.
a(n)=sum{k=0..floor(n/2); C(n, 2k)4^(n-2k) }
E.g.f. : exp(4x)cosh(x) - Paul Barry (pbarry(AT)wit.ie), Oct 06 2004
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CROSSREFS
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Cf. A005059.
Sequence in context: A117439 A081910 A026773 this_sequence A005572 A081922 A124325
Adjacent sequences: A081183 A081184 A081185 this_sequence A081187 A081188 A081189
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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), Mar 11 2003
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