cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A277429 Numerators of the Fabius function F(3/2^n).

Original entry on oeis.org

67, 73, 46657, 25219, 29407171, 10997359, 109661317247, 31733679209, 558462830097043, 132566737763827, 646476041042787542443, 130499244418507180561, 2411172049639892707896547, 424191560077453917728503, 84883189962706557116984038531, 172244289373664036915914887721
Offset: 2

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Author

Vladimir Reshetnikov, Oct 14 2016

Keywords

Comments

The Fabius function F(x) is the smooth monotone increasing function on [0, 1] satisfying F(0) = 0, F(1) = 1, F'(x) = 2*F(2*x) for 0 < x < 1/2, F'(x) = 2*F(2*(1-x)) for 1/2 < x < 1. It is infinitely differentiable at every point in the interval, but is nowhere analytic. It assumes rational values at dyadic rationals.

Examples

			A277429/A277430 = 67/72, 73/288, 46657/2073600, 25219/33177600, 29407171/2809213747200, ... (starting from n = 2)
		

References

  • Rvachev V. L., Rvachev V. A., Non-classical methods of the approximation theory in boundary value problems, Naukova Dumka, Kiev (1979) (in Russian), pages 117-125.

Crossrefs

Cf. A277430 (denominators), A272755, A272757, A272343.

Programs

  • Mathematica
    c[0] = 1;
    c[k_] := c[k] = Sum[((-1)^(k - r) c[r])/(1 + 2 k - 2 r)!, {r, 0, k - 1}]/(4^k - 1);
    t[n_] := Mod[2 n + Sum[(-1)^Binomial[n, k], {k, 1, n}], 3];
    f[x_] := Module[{k = Numerator[x], n = Log2[Denominator[x]]}, Sum[((-1)^(q + t[p - 1]) 2^(-(n - 1) n/2) (1/2 - p + k)^(n - 2 q) c[q])/(4^q (n - 2 q)!), {p, 1, k}, {q, 0, n/2}]];
    Table[Numerator[f[3/2^n]], {n, 2, 20}]
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