OFFSET
2,5
COMMENTS
Old name: A dihedral D1 elliptical transform on A000073.
A D1 elliptical invariant transform leaves the ratio unchanged.
FORMULA
Conjectures from Chai Wah Wu, Dec 21 2023: (Start)
a(n) = a(n-2) + 2*a(n-3) + 2*a(n-4) + 2*a(n-5) + 2*a(n-6) + 2*a(n-7) + 3*a(n-8) + 2*a(n-9) + a(n-10) for n > 11.
G.f.: x^4*(-x^2 - x - 1)/((x + 1)*(x^2 + 1)*(x^4 + 1)*(x^3 + x^2 + x - 1)). (End)
For n >= 5, a(n) = a(n-1) + a(n-2) + a(n-3) - A132151(n+2). - Peter Munn, Jul 17 2025
MATHEMATICA
g[x_] = (x - 1)^2/(-4*x) M = {{0, 1, 0}, {0, 0, 1}, {1, 1, 1}} w[0] = {0, 1, 1}; w[n_] := w[n] = M.w[n - 1] a0 = Table[ -Floor[g[w[n][[1]]]], {n, 1, 25}] b0 = Table[N[a0[[n + 1]]/a0[[n]]], {n, 2, 24}]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Roger L. Bagula, Mar 13 2006
EXTENSIONS
Edited by Peter Munn, Jul 17 2025
STATUS
approved