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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A170923 a(n) = denominator of the coefficient c(n) of x^n in sqrt(1+x)/Product_{k=1..n-1} 1 + c(k)*x^k, n = 1, 2, 3, ...

Original entry on oeis.org

2, 8, 8, 128, 32, 512, 128, 32768, 128, 32768, 2048, 2097152, 8192, 2097152, 32768, 2147483648, 131072, 16777216, 524288, 34359738368, 2097152, 8589934592, 8388608, 35184372088832, 524288, 549755813888, 33554432, 562949953421312, 536870912, 35184372088832
Offset: 1

Views

Author

N. J. A. Sloane, Jan 31 2010

Keywords

Crossrefs

Cf. A170922 (numerators).
Cf. A353583 / A353584 for power product expansion of 1 + tan x.
Cf. A353586 / A353587 for power product expansion of (tan x)/x.

Programs

  • Maple
    L := 32: g := NULL:
    t := series(sqrt(1+x), x, L):
    for n from 1 to L-2 do
       c := coeff(t, x, n);
       t := series(t/(1 + c*x^n), x, L);
       g := g, c;
    od: map(denom, [g]); # Peter Luschny, May 12 2022

Extensions

Following a suggestion from Ilya Gutkovskiy, name corrected so that it matches the data by Peter Luschny, May 12 2022
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