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A247416 Number of friezes of type B_n. 1

%I #14 Sep 17 2014 11:51:01

%S 2,6,21,75,273,1008,3762,14158,53635,204270,781378,2999906,11553234,

%T 44612760,172671925,669679793,2601913466,10125418060,39459828905,

%U 153977743500,601545298200,2352559491900,9209476821105,36084150102001,141499349638556,555292275455022,2180689496523468,8569380062230708

%N Number of friezes of type B_n.

%H B. Fontaine and P.-G. Plamondon, <a href="http://arxiv.org/abs/1409.3698">Counting friezes in type D_n</a>, arXiv:1409.3698 [math.CO], 2014.

%F a(n) = sum_{m=1..floor(sqrt(n+1))} binomial(2n-m^2+1,n).

%o (PARI) a(n) = sum(m=1,sqrtint(n+1), binomial(2*n-m^2+1,n) ); \\ _Joerg Arndt_, Sep 16 2014

%Y Cf. A000108, A000984 and A247415, the number of friezes of type A_n, C_n and D_n.

%K nonn

%O 1,1

%A _Bruce Fontaine_, Sep 16 2014

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Last modified March 19 01:34 EDT 2024. Contains 370952 sequences. (Running on oeis4.)