|
|
A027070
|
|
a(n) = diagonal sum of right-justified array T given by A027052.
|
|
2
|
|
|
1, 1, 1, 4, 6, 12, 31, 73, 183, 476, 1248, 3322, 8943, 24271, 66355, 182538, 504824, 1402682, 3913585, 10959499, 30792445, 86775340, 245204312, 694603032, 1972115945, 5610955925, 15994866669, 45677496204, 130661330526, 374339736820, 1074025873959, 3085699969569, 8876601230175
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
0,4
|
|
LINKS
|
|
|
FORMULA
|
|
|
MAPLE
|
T:= proc(n, k) option remember;
if k<0 or k>2*n then 0
elif k=0 or k=2 or k=2*n then 1
elif k=1 then 0
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..35); # G. C. Greubel, Nov 06 2019
|
|
MATHEMATICA
|
T[n_, k_]:= T[n, k]= If[k<0 || k>2*n, 0, If[k==0 || k==2 || k==2*n, 1, If[k==1, 0, Sum[T[n-1, k-j], {j, 3}]]]]; Table[Sum[T[n-k, 2*n-3*k], {k, 0, n}], {n, 0, 35}] (* G. C. Greubel, Nov 06 2019 *)
|
|
PROG
|
(Sage)
@CachedFunction
def T(n, k):
if (k<0 or k>2*n): return 0
elif (k==0 or k==2 or k==2*n): return 1
elif (k==1): return 0
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..35)] # G. C. Greubel, Nov 06 2019
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|