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A027048
a(n) = Sum_{k=0..2n-2} T(n,k) * T(n,k+2), with T given by A027023.
2
5, 29, 213, 1633, 12821, 102369, 826305, 6724933, 55108961, 454279229, 3764205941, 31334121045, 261903891425, 2197181330193, 18494163039793, 156140262436597, 1321876222268977, 11219183496737037, 95441562533950341, 813656964557564557, 6950294796825730249
OFFSET
2,1
LINKS
MAPLE
T:= proc(n, k) option remember;
if k<3 or k=2*n then 1
else add(T(n-1, k-j), j=1..3)
fi
end:
seq(add(T(n, k)*T(n, k+2), k=0..2*n-2), n=2..30); # G. C. Greubel, Nov 04 2019
MATHEMATICA
T[n_, k_]:= T[n, k]= If[k<3 || k==2*n, 1, Sum[T[n-1, k-j], {j, 3}]]; Table[Sum[T[n, k]*T[n, k+2], {k, 0, 2*n-2}], {n, 2, 30}] (* G. C. Greubel, Nov 04 2019 *)
PROG
(Sage)
@CachedFunction
def T(n, k):
if (k<3 or k==2*n): return 1
else: return sum(T(n-1, k-j) for j in (1..3))
[sum(T(n, k)*T(n, k+2) for k in (0..2*n-2)) for n in (2..30)] # G. C. Greubel, Nov 04 2019
CROSSREFS
Sequence in context: A030522 A091124 A121143 * A356408 A192463 A243952
KEYWORD
nonn
EXTENSIONS
More terms from Sean A. Irvine, Oct 22 2019
STATUS
approved