A027035 a(n) = Sum_{k=0..n} T(n,n+k), T given by A027023.

1, 2, 5, 14, 39, 112, 323, 932, 2693, 7790, 22565, 65466, 190243, 553748, 1614363, 4713432, 13780841, 40343210, 118243273, 346937614, 1018958151, 2995407840, 8812890391, 25948662684, 76457517949, 225429675606, 665069604713

Offset

0,2

Links

G. C. Greubel, Table of n, a(n) for n = 0..1000

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), k=n..2*n), n=0..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], {k, n, 2*n}], {n, 0, 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) for k in (n..2*n)) for n in (0..30)] # G. C. Greubel, Nov 04 2019

Crossrefs

Sequence in context: A201778 A367655 A105641 * A102406 A307754 A151409

Adjacent sequences: A027032 A027033 A027034 * A027036 A027037 A027038

Keyword

nonn

Author

Clark Kimberling

Status

approved