OFFSET
1,2
LINKS
B. Fontaine and P.-G. Plamondon, Counting friezes in type D_n, arXiv:1409.3698 [math.CO], 2014.
FORMULA
a(n) = sum_{m=1..n} A000005(m)*binomial(2n-m-1,n-m).
MAPLE
a:= n -> add(numtheory:-tau(m)*binomial(2*n-m-1, n-m), m=1..n):
seq(a(n), n=1..100); # Robert Israel, Sep 17 2014
MATHEMATICA
a[n_] := Sum[DivisorSigma[0, m] Binomial[2n-m-1, n m], {m, 1, n}]
Array[a, 29] (* Jean-François Alcover, Sep 18 2018 *)
PROG
(PARI) a(n) = sum(m=1, n, numdiv(m)*binomial(2*n-m-1, n-m) ); \\ Joerg Arndt, Sep 16 2014
CROSSREFS
KEYWORD
nonn
AUTHOR
Bruce Fontaine, Sep 16 2014
STATUS
approved