Search: id:A154325
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%I A154325
%S A154325 1,1,1,1,2,1,1,2,2,1,1,2,2,2,1,1,2,2,2,2,1,1,2,2,2,2,2,1,1,2,2,2,2,2,2,
%T A154325 1,1,2,2,2,2,2,2,2,1,1,2,2,2,2,2,2,2,2,1,1,2,2,2,2,2,2,2,2,2,1
%N A154325 Triangle with interior all 2's and borders 1.
%C A154325 This triangle follows a general construction method as follows: Let a(n) 
               be an integer sequence
%C A154325 with a(0)=1, a(1)=1. Then T(n,k,r):=[k<=n](1+r*a(k)*a(n-k)) defines a 
               symmetrical triangle.
%C A154325 Row sums are n+1+r*sum{k=0..n, a(k)*a(n-k)} and central coefficients 
               are 1+r*a(n)^2.
%C A154325 Here a(n)=1-0^n and r=1. Row sums are A004277.
%C A154325 Eigensequence of the triangle = A000129, the Pell sequence. [From Gary 
               W. Adamson (qntmpkt(AT)yahoo.com), Feb 12 2009]
%F A154325 Number triangle T(n,k)=[k<=n](2-0^(n-k)-0^k+0^(n+k))=[k<=n](2-0^(k(n-k))).
%F A154325 a(n) = 2 - A103451(n). [From Omar E. Pol (info(AT)polprimos.com), Jan 
               18 2009]
%e A154325 Triangle begins
%e A154325 1,
%e A154325 1, 1,
%e A154325 1, 2, 1,
%e A154325 1, 2, 2, 1,
%e A154325 1, 2, 2, 2, 1,
%e A154325 1, 2, 2, 2, 2, 1,
%e A154325 1, 2, 2, 2, 2, 2, 1
%Y A154325 Cf. A129765. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jan 14 
               2009]
%Y A154325 Cf. A103451. [From Omar E. Pol (info(AT)polprimos.com), Jan 18 2009]
%Y A154325 A000129 [From Gary W. Adamson (qntmpkt(AT)yahoo.com), Feb 12 2009]
%Y A154325 Sequence in context: A023589 A134034 A157415 this_sequence A129765 A143187 
               A143209
%Y A154325 Adjacent sequences: A154322 A154323 A154324 this_sequence A154326 A154327 
               A154328
%K A154325 easy,nonn,tabl
%O A154325 0,5
%A A154325 Paul Barry (pbarry(AT)wit.ie), Jan 07 2009

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