OFFSET
0,2
COMMENTS
First differences of A238147.
LINKS
T. Khovanova and J. Xiong, Nim Fractals, arXiv:1405.594291 [math.CO] (2014), p. 17 and J. Int. Seq. 17 (2014) # 14.7.8.
FORMULA
a(2n+1) = 10*a(n), a(2n+2) = a(n+1) + 5*a(n).
EXAMPLE
The P-positions with the total of 4 are permutations of (0,0,0,2,2) and (0,1,1,1,1). Therefore, a(2)=15.
MATHEMATICA
Table[Length[
Select[Flatten[
Table[{n, k, j, i, BitXor[n, k, j, i]}, {n, 0, a}, {k, 0, a}, {j,
0, a}, {i, 0, a}], 3], Total[#] == a &]], {a, 0, 90, 2}]
(* Second program: *)
(* b = A238147 *) b[n_] := b[n] = Which[n <= 1, {1, 11}[[n+1]], OddQ[n], 11 b[(n-1)/2] + 5 b[(n-1)/2 - 1], EvenQ[n], b[(n-2)/2 + 1] + 15 b[(n-2)/2]];
Join[{1}, Differences[Array[b, 40, 0]]] (* Jean-François Alcover, Dec 14 2018 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Tanya Khovanova and Joshua Xiong, May 02 2014
STATUS
approved