Search: id:A100227
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%I A100227
%S A100227 1,1,5,13,33,81,197,477,1153,2785,6725,16237,39201,94641,228485,551613,
%T A100227 1331713,3215041,7761797,18738637,45239073,109216785,263672645,
%U A100227 636562077,1536796801,3710155681,8957108165,21624372013,52205852193
%N A100227 Main diagonal of triangle A100226.
%F A100227 a(n) = 2*a(n-1) + a(n-2) + 2 for n>1, with a(0)=1, a(1)=1. G.f.: Sum_{n>
               =1} a(n)*x^n/n = log((1-x)/(1-2*x-x^2)).
%F A100227 G.f.: (1-2*x+3*x^2)/(1-3*x+x^2+x^3). - Paul D. Hanna (pauldhanna(AT)juno.com), 
               Feb 22 2005
%o A100227 (PARI) a(n)=if(n==0,1,n*polcoeff(log((1-x)/(1-2*x-x^2)+x*O(x^n)),n))
%o A100227 (PARI) a(n)=polcoeff((1-2*x+3*x^2)/(1-3*x+x^2+x^3)+x*O(x^n),n) (Hanna)
%Y A100227 Cf. A100225, A100226.
%Y A100227 Equals A002203(n) - 1.
%Y A100227 Sequence in context: A146924 A001981 A141025 this_sequence A027051 A109786 
               A055426
%Y A100227 Adjacent sequences: A100224 A100225 A100226 this_sequence A100228 A100229 
               A100230
%K A100227 nonn
%O A100227 0,3
%A A100227 Paul D. Hanna (pauldhanna(AT)juno.com), Nov 29 2004

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