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.

Showing 1-3 of 3 results.

A170927 Consider the 2^n values of A139250(i)/i^2 for 2^n <= i < 2^(n+1); a(n) = value of i where this quantity is minimized.

Original entry on oeis.org

1, 2, 5, 12, 21, 44, 89, 180, 362, 728, 1459, 2921, 5843, 11690, 23384, 46770, 93544, 187094, 374193, 748391, 1496786, 2993576, 5987158, 11974321, 23948647, 47897300, 95794608, 191589222, 383178450, 766356910, 1532713828, 3065427664, 6130855333, 12261710675
Offset: 0

Views

Author

Benoit Jubin, Jan 22 2010, Feb 06 2010

Keywords

Comments

{log_2 a(n)} converges to about 0.513441 and equivalently 2^{log_2 a(n)}-1 converges to about 1.427451, and the corresponding values T(i)/i^2 converge to about 0.4513058.
For all values listed, a(n) = 2 * a(n-1) + c(n), where c(n) is a small positive integer, except for a(4) where c(4)=-3. - Robert Price, Aug 16 2015

Examples

			The values of A139250(i)/i^2 for i = 1 .., 15 are 1.0, 0.7500000000, 0.7777777778, 0.6875000000, 0.6000000000, 0.6388888889, 0.7142857143, 0.6718750000, 0.5802469136, 0.5500000000, 0.5537190083, 0.5486111111, 0.5621301775, 0.6275510204, 0.6888888889, 0.6679687500. The minimal value for 4 <= i <= 7 is 0.6000000000 at i=5.
		

Crossrefs

Extensions

a(26)-a(33) from Robert Price, Aug 18 2012

A261895 Decimal expansion of the lower limit of A162795(i)/i^2.

Original entry on oeis.org

2, 2, 5, 6, 5, 2, 9, 1, 4, 2
Offset: 0

Views

Author

Robert Price, Sep 05 2015

Keywords

Comments

Sequence suggested by Omar E. Pol.
Similar to the constant mentioned in the Applegate-Pol-Sloane article, Section 5, the fractal-like structure. It is also mentioned in A139250 and A170927.
It appears that this sequence is a quarter of A261313 and half of A195853.

Examples

			0.2256529142...
		

References

  • D. Applegate, Omar E. Pol and N. J. A. Sloane, The Toothpick Sequence and Other Sequences from Cellular Automata, Congressus Numerantium, Vol. 206 (2010), 157-191

Crossrefs

Programs

  • Mathematica
    T = 1; t[0] = 0; t[1] = 1; lst = {1};
    Do[twon = 2^n; Tmin = 1; imin = 1;
        Do[If[i == twon, t[i] = twon,
                         t[i] = 2*t[i - twon] + t[i - twon + 1];
                         If[OddQ[i], T = T + t[i];
                                     Ttest = T/(i*i)];
                                     If[ Ttest
    				

A261896 Consider the 2^n values of A162795(i)/i^2 for 2^n <= i < 2^(n+1); a(n) = value of i where this quantity is minimized.

Original entry on oeis.org

3, 5, 11, 25, 43, 89, 179, 361, 727, 1459, 2921, 5843, 11689, 23383, 46769, 93543, 187093, 374193, 748391, 1496785, 2993575, 5987157, 11974321, 23948647, 47897299, 95794607, 191589221, 383178449, 766356903, 1532713827, 3065427663, 6130855333, 12261710675, 24523421357, 49046842723
Offset: 0

Views

Author

Robert Price, Sep 05 2015

Keywords

Comments

Sequence suggested by Omar E. Pol.
Note that all values in this sequence are odd and that a(n) is approximately 2*a(n-1).

References

  • D. Applegate, O. E. Pol and N. J. A. Sloane, The toothpick sequence and other sequences from cellular automata, Congressus Numerantium, v. 206 (2010) 157-191.

Crossrefs

Programs

  • Mathematica
    T = 1; t[0] = 0; t[1] = 1; lst = {1};
    Do[twon = 2^n; Tmin = 1; imin = 1;
        Do[If[i==twon, t[i]=twon,
                       t[i]=2*t[i-twon]+t[i-twon+1];
                       If[OddQ[i], T=T+t[i];
                                   Ttest=T/(i*i)];
                                   If[Ttest
    				
Showing 1-3 of 3 results.