Search: id:A052937 Results 1-1 of 1 results found. %I A052937 %S A052937 2,3,6,13,30,71,170,409,986,2379,5742,13861,33462,80783,195026,470833, %T A052937 1136690,2744211,6625110,15994429,38613966,93222359,225058682, %U A052937 543339721,1311738122,3166815963,7645370046,18457556053,44560482150 %N A052937 A simple regular expression. %H A052937 INRIA Algorithms Project, Encyclopedia of Combinatorial Structures 928 %F A052937 G.f.: -(-2+3*x+x^2)/(-1+x)/(-1+2*x+x^2) %F A052937 Recurrence: {a(2)=6, a(1)=3, a(0)=2, -a(n)-2*a(n+1)+a(n+2)+2} %F A052937 1+Sum(1/4*(1+_alpha)*_alpha^(-1-n), _alpha=RootOf(-1+2*_Z+_Z^2)) %F A052937 a(n) = A000129(n+1)+1, where A000129 are the Pell Numbers. - Graeme McRae (g_m(AT)mcraefamily.com), Aug 03 2006 %p A052937 spec := [S,{S=Union(Sequence(Z),Sequence(Union(Z,Z,Prod(Z,Z))))},unlabeled ]: seq(combstruct[count ](spec, size=n), n=0..20); %Y A052937 Cf. A001333. %Y A052937 Sequence in context: A107316 A124682 A079512 this_sequence A005554 A077212 A076836 %Y A052937 Adjacent sequences: A052934 A052935 A052936 this_sequence A052938 A052939 A052940 %K A052937 easy,nonn %O A052937 0,1 %A A052937 encyclopedia(AT)pommard.inria.fr, Jan 25 2000 %E A052937 More terms from James A. Sellers (sellersj(AT)math.psu.edu), Jun 05 2000 Search completed in 0.001 seconds