OFFSET
1,2
COMMENTS
Start with A = [[[1]]], iteratively replace every element Aijk with Aijk * [[[1, 1], [1, 1]], [[1, 1], [1, 0]]]. a(n) is the sum of the resulting array inside the cubic region i, j, k < n. - Peter Karpov, Mar 01 2016
a(n) is a lower bound on A268239. - Peter Karpov, Mar 01 2016
LINKS
Peter Karpov, InvMem, Item 21
FORMULA
a(1) = 1, a(2*n) = 7*a(n), a(2*n+1) = 4*a(n+1) + 3*a(n) - 6*A080100(2*n+1).
MATHEMATICA
a[n_] := If[Mod[n, 2] == 0, 7 a[n/2], 4 a[(n + 1)/2] + 3 a[(n - 1)/2] - 6 * 2^DigitCount[n, 2, 0]]; a[1] := 1;
Table[a[i], {i, 1, 40}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Peter Karpov, Mar 01 2016
STATUS
approved