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A327134 The number of monomials in a strong elliptic divisibility sequence t_n in free variables x, y, z. 0
0, 1, 1, 1, 1, 2, 3, 3, 4, 7, 9, 11, 14, 20, 27, 34, 40, 53, 68, 80, 94, 121, 145, 169, 197, 236, 279, 322, 362, 426, 494, 555, 622, 717, 810, 904, 1003, 1132, 1266, 1402, 1534, 1712, 1898, 2073, 2256, 2497, 2733, 2969, 3215, 3515, 3825, 4135, 4440, 4826, 5222 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,6
LINKS
Clark Kimberling, Strong divisibility sequences and some conjectures, Fib. Quart., 17 (1979), 13-17.
EXAMPLE
t_1 = 1, t_2 = x, t_3 = y, t_4 = x*z, a(1) = a(2) = a(3) = a(4) = 1, t_5 = x^4*z - y^3, a(5) = 2. t_6 = x^5*y*z - x*y^4 - x*y*z^2, a(6) = 3. t_7 = x^4*y^3*z - x^4*z^3 - y^6, a(7) = 3.
MATHEMATICA
a[ n_] := a[n] = If[ Abs@n <= 4, Boole[n != 0], Length @ t[n]]; t[ n_] := t[n] = Sign[n] If[ Abs@n <= 4, {0, 1, x, y, x z}[[Abs[n] + 1]], (x^2 t[n-1] t[n-3] - y t[n-2]^2) / t[n-4] // Factor // Expand];
CROSSREFS
Sequence in context: A154309 A249579 A329301 * A140514 A240209 A047079
KEYWORD
nonn
AUTHOR
Michael Somos, Nov 28 2019
STATUS
approved

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Last modified April 15 00:51 EDT 2024. Contains 371667 sequences. (Running on oeis4.)