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A146965 a(n) = 10*a(n-1) - 18*a(n-2) with a(0)=1, a(1)=5. 2

%I #25 Sep 08 2022 08:45:38

%S 1,5,32,230,1724,13100,99968,763880,5839376,44643920,341330432,

%T 2609713760,19953189824,152557050560,1166413088768,8918103977600,

%U 68185604178176,521330170184960,3985960826642432,30475665203095040

%N a(n) = 10*a(n-1) - 18*a(n-2) with a(0)=1, a(1)=5.

%C The Mathematica program implements the formula provided by Deleham and Brockhaus. - _Harvey P. Dale_, Feb 17 2011

%H Vincenzo Librandi, <a href="/A146965/b146965.txt">Table of n, a(n) for n = 0..145</a>

%H <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (10,-18).

%F a(n) = ((5 + sqrt(7))^n + (5 - sqrt(7))^n)/2.

%F G.f.: (1-5*x)/(1-10*x+18*x^2). - _Philippe Deléham_ and _Klaus Brockhaus_, Nov 05 2008

%F a(n) = (Sum_{k=0..n} A098158(n,k)*5^(2*k)*7^(n-k))/5^n. - _Philippe Deléham_, Nov 06 2008

%F E.g.f.: exp(5*x)*cosh(sqrt(7)*x). - _G. C. Greubel_, Jan 08 2020

%p seq(coeff(series((1-5*x)/(1-10*x+18*x^2), x, n+1), x, n), n = 0..30); # _G. C. Greubel_, Jan 08 2020

%t Transpose[NestList[{#[[2]],10#[[2]]-18#[[1]]}&,{1,5},20]][[1]] (* _Harvey P. Dale_, Feb 17 2011 *)

%t LinearRecurrence[{10,-18},{1,5},30] (* _Harvey P. Dale_, Aug 27 2013 *)

%o (Magma) Z<x>:= PolynomialRing(Integers()); N<r7>:=NumberField(x^2-7); S:=[ ((5+r7)^n+(5-r7)^n)/2: n in [0..19] ]; [ Integers()!S[j]: j in [1..#S] ]; // _Klaus Brockhaus_, Nov 05 2008

%o (PARI) my(x='x+O('x^30)); Vec((1-5*x)/(1-10*x+18*x^2)) \\ _G. C. Greubel_, Jan 08 2020

%o (Sage)

%o def A146965_list(prec):

%o P.<x> = PowerSeriesRing(ZZ, prec)

%o return P( (1-5*x)/(1-10*x+18*x^2) ).list()

%o A146965_list(30) # _G. C. Greubel_, Jan 08 2020

%o (GAP) a:=[1,5];; for n in [3..30] do a[n]:=10*a[n-1]-18*a[n-2]; od; a; # _G. C. Greubel_, Jan 08 2020

%K nonn

%O 0,2

%A Al Hakanson (hawkuu(AT)gmail.com), Nov 03 2008

%E Extended beyond a(7) by _Klaus Brockhaus_, Nov 05 2008

%E Name from _Philippe Deléham_ and _Klaus Brockhaus_, Nov 05 2008

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Last modified March 29 00:26 EDT 2024. Contains 371264 sequences. (Running on oeis4.)