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A014921
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a(1)=1, a(n) = n*8^(n-1) + a(n-1).
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2
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1, 17, 209, 2257, 22737, 219345, 2054353, 18831569, 169826513, 1512003793, 13323163857, 116402378961, 1009755576529, 8706336970961, 74677034637521, 637626988058833, 5422701592139985, 45955098238474449
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OFFSET
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1,2
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LINKS
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FORMULA
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E.g.f.: (exp(x) + exp(8*x)*(56*x - 1))/49. - Iain Fox, Aug 10 2018
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MAPLE
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a:=n->sum (8^n-8^j, j=0..n): seq(a(n)/7, n=1..21); # Zerinvary Lajos, Dec 14 2008
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MATHEMATICA
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CoefficientList[Series[1/((1 - x)(1 - 8*x)^2), {x, 0, 40}], x] (* Vincenzo Librandi, Oct 23 2012 *)
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PROG
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(Magma) I:=[1, 17]; [n le 2 select I[n] else 16*Self(n-1)-64*Self(n-2)+1: n in [1..30]]; // Vincenzo Librandi, Oct 23 2012
(PARI) first(n) = my(res=vector(n)); res[1]=1; for(x=2, n, res[x]=x*8^(x-1)+res[x-1]); res \\ Iain Fox, Aug 10 2018
(PARI) a(n) = (1 + 8^n*(7*n-1))/49 \\ Iain Fox, Aug 10 2018
(PARI) first(n) = Vec(x/((1-x)*(1-8*x)^2) + O(x^(n+1))) \\ Iain Fox, Aug 10 2018
(GAP) a:=[1];; for n in [2..20] do a[n]:=n*8^(n-1)+a[n-1]; od; a; # Muniru A Asiru, Aug 12 2018
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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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