OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..750
FORMULA
a(n) = Sum_{k=0..n} T(n-k, 2*n-3*k), where T = A027023. - G. C. Greubel, Nov 05 2019
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, 2*n-3*k), k=0..n), n=0..30); # G. C. Greubel, Nov 05 2019
MATHEMATICA
T[n_, k_]:= T[n, k]= If[n<0, 0, If[k<3 || k==2*n, 1, Sum[T[n-1, k-j], {j, 3}]]]; Table[Sum[T[n-k, 2*n-3*k], {k, 0, n}], {n, 0, 30}] (* G. C. Greubel, Nov 05 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, 2*n-3*k) for k in (0..n)) for n in (0..30)] # G. C. Greubel, Nov 05 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved