cp's OEIS Frontend

A244473 3rd-largest term in n-th row of Stern's diatomic triangle A002487.

%I A244473 #18 Jul 10 2015 08:44:00
%S A244473 1,3,5,11,18,30,49,80,129,209,338,547,885,1432,2317,3749,6066,9815,
%T A244473 15881,25696,41577,67273,108850,176123,284973,461096,746069,1207165,
%U A244473 1953234,3160399,5113633,8274032,13387665,21661697,35049362,56711059,91760421
%N A244473 3rd-largest term in n-th row of Stern's diatomic triangle A002487.
%H A244473 Colin Barker, <a href="/A244473/b244473.txt">Table of n, a(n) for n = 2..1000</a>
%H A244473 Jennifer Lansing, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL17/Lansing/lansing2.html">Largest Values for the Stern Sequence</a>, J. Integer Seqs., 17 (2014), #14.7.5.
%H A244473 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (1,1).
%F A244473 a(n) = a(n-1)+a(n-2) for n>9. - _Colin Barker_, Jul 10 2015
%F A244473 G.f.: -x^2*(x^7+x^6+x^5+2*x^4+3*x^3+x^2+2*x+1) / (x^2+x-1). - _Colin Barker_, Jul 10 2015
%p A244473 A244473 := proc(n)
%p A244473     if n < 8 then
%p A244473         op(n,[-1,1,3,5,11,18,30]) ;
%p A244473     else
%p A244473         combinat[fibonacci](n+1)+5*combinat[fibonacci](n-4) ;
%p A244473     end if;
%p A244473 end proc:
%p A244473 seq(A244473(n),n=2..50) ; # _R. J. Mathar_, Jul 05 2014
%t A244473 Join[{1,3,5,11,18,30},LinearRecurrence[{1,1},{49,80},40]] (* _Harvey P. Dale_, Jan 13 2015 *)
%o A244473 (PARI) Vec(-x^2*(x^7+x^6+x^5+2*x^4+3*x^3+x^2+2*x+1)/(x^2+x-1) + O(x^100)) \\ _Colin Barker_, Jul 10 2015
%Y A244473 Cf. A002487, A244472-A244476.
%K A244473 nonn,easy
%O A244473 2,2
%A A244473 _N. J. A. Sloane_, Jul 01 2014