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A027049
a(n) = Sum_{k=0..2n-3} T(n,k) * T(n,k+3), with T given by A027023.
2
16, 120, 952, 7848, 65580, 550476, 4631876, 39047764, 329784608, 2790469092, 23656401612, 200928615160, 1709781846028, 14575407966156, 124466311279620, 1064636218853556, 9120848372291680, 78256468639080460, 672393605270681188, 5785139333187494936, 49838058776228021388
OFFSET
3,1
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+3), k=0..2*n-3), n=3..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+3], {k, 0, 2*n-3}], {n, 3, 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+3) for k in (0..2*n-3)) for n in (3..30)] # G. C. Greubel, Nov 04 2019
CROSSREFS
Sequence in context: A324066 A164542 A351383 * A060219 A185760 A301649
KEYWORD
nonn
EXTENSIONS
More terms from Sean A. Irvine, Oct 22 2019
STATUS
approved