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%I A026861 #15 Apr 09 2023 23:04:58
%S A026861 1,5,22,95,411,1790,7855,34725,154573,692450,3120206,14135555,
%T A026861 64356345,294341325,1351889910,6233399525,28845511125,133933280000,
%U A026861 623811120960,2913924782375,13648296620445,64087737455725,301644762913977
%N A026861 T(2n,n+1), T given by A026747.
%C A026861 a(n+1) = p(n+1) where p(x) is the unique degree-n polynomial such that p(k) = A002212(k+1) for k=0,1,...,n. - _Michael Somos_, Oct 07 2003
%C A026861 Number of skew Dyck paths of semilength n+1 containing at least one left step. - _David Scambler_, Jun 17 2013
%F A026861 a(n) = A002212(n+1) - A000108(n+1). - _David Scambler_, Jun 17 2013
%o A026861 (PARI) a(n)=if(n<1,0,subst(polinterpolate(Vec((1-3*x-sqrt(1-6*x+5*x^2+x^2*O(x^n)))/2)),x,n+1))
%Y A026861 Cf. A000108, A002212, A026747.
%K A026861 nonn
%O A026861 1,2
%A A026861 _Clark Kimberling_

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