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A275209 Expansion of (A(x)^2+A(x^2))/2 where A(x) = A001006(x)-1. 2
0, 0, 1, 2, 7, 17, 49, 129, 358, 970, 2679, 7364, 20414, 56634, 157877, 441084, 1236496, 3474672, 9790403, 27648486, 78256907, 221951037, 630723367, 1795576937, 5120487946, 14625574662, 41837955145, 119851980508, 343798121799, 987445317761, 2839518519233 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,4
COMMENTS
Analog of A274934 with Motzkin numbers replacing connected graph counts.
LINKS
FORMULA
a(2n+1) = A275210(2n+1).
MAPLE
b:= proc(n) option remember; `if`(n<2, 1,
((3*(n-1))*b(n-2)+(1+2*n)*b(n-1))/(n+2))
end:
a:= proc(n) option remember; add(b(j)*b(n-j), j=1..n/2)-
`if`(n::odd, 0, (t->t*(t-1)/2)(b(n/2)))
end:
seq(a(n), n=0..40); # Alois P. Heinz, Jul 19 2016
MATHEMATICA
b[n_] := b[n] = If[n<2, 1, ((3*(n-1))*b[n-2] + (1+2*n)*b[n-1])/(n+2)];
a[n_] := a[n] = Sum[b[j]*b[n-j], {j, 1, n/2}] - If[OddQ[n], 0, Function[t, t*(t - 1)/2][b[n/2]]];
Table[a[n], {n, 0, 40}] (* Jean-François Alcover, May 16 2017, after Alois P. Heinz *)
CROSSREFS
Cf. A275210.
Sequence in context: A367687 A085411 A180665 * A007049 A133407 A182667
KEYWORD
nonn
AUTHOR
R. J. Mathar, Jul 19 2016
STATUS
approved

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Last modified May 23 17:39 EDT 2024. Contains 372765 sequences. (Running on oeis4.)