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.

A067410 Triangle with columns built from certain power sequences.

Original entry on oeis.org

1, 2, 1, 4, 3, 1, 8, 12, 4, 1, 16, 48, 24, 5, 1, 32, 192, 144, 40, 6, 1, 64, 768, 864, 320, 60, 7, 1, 128, 3072, 5184, 2560, 600, 84, 8, 1, 256, 12288, 31104, 20480, 6000, 1008, 112, 9, 1, 512, 49152, 186624, 163840, 60000, 12096, 1568, 144, 10, 1
Offset: 0

Views

Author

Wolfdieter Lang, Jan 25 2002

Keywords

Examples

			Triangle starts:
  1;
  2,  1;
  4,  3, 1;
  8, 12, 4, 1;
  ...
		

Crossrefs

Cf. A009998 (triangle built from powers of (m+1)), A067402.

Programs

  • Mathematica
    A[n_,m_]:=If[n==m,1,(m+2)(2(m+1))^(n-m-1)]; Flatten[Table[A[n,m],{n,0,9},{m,0,n}]] (* Stefano Spezia, Sep 30 2022 *)

Formula

a(n, m) = 1 if n = m; a(n, m) = (m+2)*(2*(m+1))^(n-m-1) if n > m >= 0.
G.f. for column m: (x^m)*(1-m*x)/(1-2*(m+1)*x).

A326811 Numbers in A326806 whose sum of digits is not a power of 10 and are not of the form 5*10^k or 6*10^k.

Original entry on oeis.org

0, 6667, 58824, 8823529412, 5263157894737, 19607843137255, 65217391304348, 98360655737705, 746268656716418, 4761904761904762, 8955223880597015, 58823529411764706, 1369863013698630137, 60240963855421686747, 3061224489795918367347, 34090909090909090909091
Offset: 1

Views

Author

Chai Wah Wu, Oct 19 2019

Keywords

Comments

A326806 = A326811 UNION A326833 UNION A090019 UNION A093143. Note that several terms (e.g. a(10), a(13), a(17)-a(19)) look like the rounding off of a periodic sequence, i.e. yxxxa9xxxa9xxxa9... rounded off to yxxxa9xxxa9xxxb, where b = a+1. Perhaps these can be considered near-cyclic numbers? - Chai Wah Wu, Oct 21 2019

Crossrefs

Extensions

More terms from Chai Wah Wu, Oct 21 2019

A346178 Expansion of (1-2*x)/(1-10*x).

Original entry on oeis.org

1, 8, 80, 800, 8000, 80000, 800000, 8000000, 80000000, 800000000, 8000000000, 80000000000, 800000000000, 8000000000000, 80000000000000, 800000000000000, 8000000000000000, 80000000000000000, 800000000000000000, 8000000000000000000, 80000000000000000000
Offset: 0

Views

Author

Felix Fröhlich, Jul 09 2021

Keywords

Crossrefs

Cf. expansion of (1-k*x)/(1-10*x) A011557 (k=0), A196662 (k=3), A090019 (k=4), A093143 (k=5), A093141 (k=6), A093138 (k=7), A093136 (k=8).

Programs

  • PARI
    Vec((1-2*x)/(1-10*x) + O(x^20))

Formula

a(n) = 8*10^(n-1), n>0.
E.g.f.: (1 + 4*exp(10*x))/5. - Stefano Spezia, Jul 09 2021
Showing 1-3 of 3 results.