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 A318245 Scaled g.f. T(v) = Sum_{n>=0} a(n)*(3*v/64)^n satisfies 9*(5*v-4)*T + d/dv(16*v*(v-1)*(3*v-4)*T') = 0, and a(0)=1; sequence gives a(n). 6
 1, 12, 180, 2928, 49860, 875952, 15754704, 288722880, 5373771876, 101334517680, 1932405892560, 37208369165760, 722497419680400, 14132680228175040, 278236490874120000, 5508974545258860288, 109624581377872629156, 2191185332414847848880, 43971545517545956240464 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The linked document "Proof Certificate" explains that period function T(v) measures precession of the J-vector along an algebraic sphere curve with local cyclic C_4 symmetry (also cf. Examples and A186375). LINKS W. G. Harter and C. W. Patterson, Rotational energy surfaces and high-J eigenvalue structure of polyatomic molecules, The Journal of Chemical Physics, 80 (1984), 4252. Bradley Klee, Proof Certificate. E. Weisstein, Goursat's Surface, Mathworld--A Wolfram Web Resource. FORMULA 3*n^2*a(n) - 4*(28*n^2-28*n+9)*a(n-1) + 64*(4*n-5)*(4*n-3)*a(n-2) = 0. For n > 0, a(n) mod 3 = 0 (conjecture, tested up to n=3*10^6). EXAMPLE Period function T_{O}(w): Take T_{C3}(u) and T_{C4}(v) from A186375 and A318245 respectively. Set (u,v)=(w-2/3,2-w), with u in [0,1/3], v in [0,1], and w in [2/3,2]. Define piecewise function T_{O}(w) = T_{C3}(w-2/3) if w in [2/3,1] or T_{O}(w) = T_{C4}(2-w) if w in [1,2]. Geometric Singular Points: Construct a family of algebraic sphere curves by intersecting a sphere 1=X^2+Y^2+Z^2 with the octahedral surface w=2*(X^4+Y^4+Z^4). Four cube vertex axes--(x+y+z, -x+y+z, x-y+z, x+y-z)--intersect the sphere in eight circular points with w=2/3. Three octahedron vertex axes--(x, y, z)--intersect the sphere in six circular points with w=2. Six cuboctahedron vertex axes--(x+y, x-y, y+z, y-z, z+x, z-x)--intersect the sphere in twelve hyperbolic points with w=1. MATHEMATICA CoefficientList[Expand[Normal@Series[Divide[Sqrt[S], Sqrt[1-4*S*x]*Sqrt[S-8 + 8*Sqrt[1-4*S*x]]], {x, 0, 13}]/.{S->12+4*Q^2}]/.{Q^n_:>(1/2)^n*Binomial[n, n/2]} /.{x->1/3*x}, x] RecurrenceTable[{3*n^2*a[n] - 4*(28*n^2-28*n+9)*a[n-1] + 64*(4*n-5)*(4*n-3)*a[n-2] == 0, a==1, a==12}, a, {n, 0, 1000}] CROSSREFS Periods: A186375, A318417. Sequence in context: A069685 A000515 A241710 * A051609 A001814 A327079 Adjacent sequences:  A318242 A318243 A318244 * A318246 A318247 A318248 KEYWORD nonn AUTHOR Bradley Klee, Aug 22 2018 STATUS approved

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Last modified July 8 03:38 EDT 2020. Contains 335504 sequences. (Running on oeis4.)