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.

Previous Showing 21-23 of 23 results.

A156134 Q_2n(sqrt(2)) (see A104035).

Original entry on oeis.org

1, 5, 157, 12425, 1836697, 436366445, 152053957237, 73053601590065, 46283414838553777, 37386890114969267285, 37503815980582784378317, 45739346519434253222582105, 66650214918099514832427062857, 114363498315755726948758209518525, 228234739109951323288351261455519397
Offset: 0

Views

Author

N. J. A. Sloane, Nov 06 2009

Keywords

Crossrefs

Cf. other sequences with a g.f. of the form cos(x)/(1 - k*sin^2(x)): A012494 (k=-1), A001209 (k=1/2), A000364(k=1), A000281 (k=2), A002437 (k=4).

Programs

  • Maple
    with(gfun):
    series(cos(x)/(1-3*sin(x)^2), x, 30):
    L := seriestolist(%):
    seq(op(2*i-1,L)*(2*i-2)!, i = 1..floor((1/2)*nops(L)));
    # Peter Bala, Feb 06 2017
  • Mathematica
    With[{nmax = 50}, CoefficientList[Series[Cos[x]/(1 - 3*Sin[x]^2), {x, 0, nmax}], x]*Range[0, nmax]!][[1 ;; ;; 2]] (* G. C. Greubel, Mar 29 2018 *)
  • PARI
    x='x+O('x^50); v=Vec(serlaplace(cos(x)/(1 - 3*sin(x)^2))); vector(#v\2,n,v[2*n-1]) \\ G. C. Greubel, Mar 29 2018

Formula

G.f. cos(x)/(1 - 3*sin(x)^2) = 1 + 5*x^2/2! + 157*x^4/4! + 12425*x^6/6! + ... - Peter Bala, Feb 06 2017

A114139 Changes in United States postal rates per ounce since 1863.

Original entry on oeis.org

-2, -2, 1, -1, 1, 1, 1, 1, 2, 2, 0, 3, 2, 3, 2, 2, 3, 4, 3, 3, 1, 1, 3, 2
Offset: 1

Views

Author

Jonathan Vos Post, Feb 03 2006

Keywords

Comments

Benjamin Franklin, first Postmaster General of the United States, applied computational complexity theory to Economics by changing the business plan for American mail by changing from payment by distance to payment by weight. "Before stamps were used a person had to collect his mail at the post office and pay for it. Franklin stopped the money loss on unclaimed mail in Philadelphia by printing in his paper the names of persons who had mail awaiting them. He also developed a simple, accurate way of keeping post-office accounts. In 1753 Franklin was made deputy postmaster general for all the colonies." [Encyclopedia Britannica]

Examples

			a(1) = -2 because the rate per half ounce was lowered effective 3 March 1863 from 3 cents to 2 cents; thereafter rates were per ounce.
		

References

  • R. K. Guy, Unsolved Problems in Number Theory, C12.

Crossrefs

A140571 Decimal expansion of the universal constant in E(h), the maximum number of essential elements of order h.

Original entry on oeis.org

2, 0, 5, 7, 2, 8, 4, 1, 2, 8, 4, 7, 8, 7, 9, 3, 4, 1, 2, 8, 5, 8, 2, 2, 3, 9, 6, 4, 4, 8, 3, 7, 6, 9, 0, 9, 1, 0, 0, 4, 3, 4, 7, 8, 2, 7, 4, 9, 4, 2, 1, 2, 6, 8, 0, 7, 4, 1, 5, 3, 8, 1, 9, 6, 6, 2, 4, 2, 3, 6, 9, 2, 9, 5, 4, 2, 7, 6, 3, 5, 1, 3, 3, 4, 9, 8, 5, 1, 9, 0, 8, 0, 7, 8, 9, 0, 1, 6, 5, 3, 6, 5, 5, 9, 7, 7
Offset: 1

Views

Author

Jonathan Vos Post, Jul 05 2008

Keywords

Comments

A fundamental result of Erdos and Graham is that every integer basis possesses only finitely many essential elements. Grekos refined this, showing that the number of essential elements in a basis or order h is bounded by a function of h only. Deschamps and Farhi (2007) proved a best possible upper bound on this function, which contains a constant whose digits are this sequence.
Abstract: Plagne recently determined the asymptotic behavior of the function E(h), which counts the maximum possible number of essential elements in an additive basis for N of order h. Here we extend his investigations by studying asymptotic behavior of the function E(h,k), which counts the maximum possible number of essential subsets of size k, in a basis of order h. For a fixed k and with h going to infinity, we show that
E(h,k) = Theta_{k} ([h^{k}/log h]^{1/(k+1)}). The determination of a more precise asymptotic formula is shown to depend on the solution of the well-known "postage stamp problem" in finite cyclic groups. On the other hand, with h fixed and k going to infinity, we show that E(h,k) ~ (h-1) (log k)/(log log k).

Examples

			2.0572841284787934...
		

Crossrefs

Programs

  • Mathematica
    RealDigits[(30*Sqrt[Log[1564]/1564]),10,120][[1]] (* Harvey P. Dale, Sep 27 2023 *)
  • PARI
    30*sqrt(log(1564)/1564) \\ Michel Marcus, Oct 18 2018

Formula

Equals 30*sqrt(log(1564)/1564).

Extensions

a(100) corrected by Georg Fischer, Jul 12 2021
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