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 1-4 of 4 results.

A048441 Take the first n numbers written in base 9, concatenate them, then convert from base 9 to base 10.

Original entry on oeis.org

1, 11, 102, 922, 8303, 74733, 672604, 6053444, 490328973, 39716646823, 3217048392674, 260580919806606, 21107054504335099, 1709671414851143033, 138483384602942585688, 11217154152838349440744, 908589486379906304700281, 73595748396772410680722779
Offset: 1

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Author

Patrick De Geest, May 15 1999

Keywords

Comments

The first two primes in this sequence occur for n = 2 (a(2) = 11) and n = 14 (a(14) = 1709671414851143033) (email from Kurt Foster, Oct 24 2015). - N. J. A. Sloane, Oct 25 2015

Examples

			a(9) = (1)(2)(3)(4)(5)(6)(7)(8)(10) = 1234567810_9 = 490328973.
		

Crossrefs

Concatenation of first n numbers in other bases: 2: A047778, 3: A048435, 4: A048436, 5: A048437, 6: A048438, 7: A048439, 8: A048440, 9: this sequence, 10: A007908, 11: A048442, 12: A048443, 13: A048444, 14: A048445, 15: A048446, 16: A048447.

Programs

  • Magma
    [n eq 1 select 1 else Self(n-1)*9^(1+Ilog(9, n))+n: n in [1..20]]; // Vincenzo Librandi, Dec 30 2012
  • Mathematica
    If[STARTPOINT==1, n={}, n=Flatten[IntegerDigits[Range[STARTPOINT-1], 9]]]; Table[AppendTo[n, IntegerDigits[w, 9]]; n=Flatten[n]; FromDigits[n, 9], {w, STARTPOINT, ENDPOINT}] (* Dylan Hamilton, Aug 11 2010 *)
    f[n_]:= FromDigits[Flatten@IntegerDigits[Range@n, 9], 9]; Array[f, 20] (* Vincenzo Librandi, Dec 30 2012 *)
  • PARI
    { cuo=0;
    for(ixp=1, 18,
    casi = ixp; cvst=0;
    while(casi != 0,
    cvd = casi%9; cvst=10*cvst + cvd + 1; casi = (casi - cvd) / 9 );
    while(cvst !=0, ptch = cvst%10;
    cuo=cuo*9+ptch-1; cvst = (cvst - ptch) / 10 ); print1(cuo, ", "))}
    \\ Douglas Latimer, Apr 27 2012
    

Extensions

More terms from Douglas Latimer, May 10 2012

A353100 a(1) = 8; for n>1, a(n) = 9 * a(n-1) + 9 - n.

Original entry on oeis.org

8, 79, 717, 6458, 58126, 523137, 4708235, 42374116, 381367044, 3432303395, 30890730553, 278016574974, 2502149174762, 22519342572853, 202674083155671, 1824066748401032, 16416600735609280, 147749406620483511, 1329744659584351589, 11967701936259164290
Offset: 1

Views

Author

Seiichi Manyama, Apr 23 2022

Keywords

Crossrefs

Programs

  • Mathematica
    LinearRecurrence[{11, -19, 9}, {8, 79, 717}, 20] (* Amiram Eldar, Apr 23 2022 *)
  • PARI
    my(N=30, x='x+O('x^N)); Vec(x*(8-9*x)/((1-x)^2*(1-9*x)))
    
  • PARI
    a(n) = (7*9^(n+1)+8*n-63)/64;
    
  • PARI
    b(n, k) = sum(j=0, n-1, (k-n+j)*k^j);
    a(n) = b(n, 9);

Formula

G.f.: x * (8 - 9 * x)/((1 - x)^2 * (1 - 9 * x)).
a(n) = 11*a(n-1) - 19*a(n-2) + 9*a(n-3).
a(n) = 7 * A014832(n) + n.
a(n) = (7*9^(n+1) + 8*n - 63)/64.
a(n) = Sum_{k=0..n-1} (9 - n + k)*9^k.
E.g.f.: exp(x)*(63*(exp(8*x) - 1) + 8*x)/64. - Stefano Spezia, May 29 2023

A002754 Related to coefficient of m in Jacobi elliptic function cn(z, m).

Original entry on oeis.org

0, 0, 4, 44, 408, 3688, 33212, 298932, 2690416, 24213776, 217924020, 1961316220, 17651846024, 158866614264, 1429799528428, 12868195755908, 115813761803232, 1042323856229152, 9380914706062436, 84428232354561996, 759854091191058040
Offset: 0

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Author

Keywords

References

  • A. Cayley, An Elementary Treatise on Elliptic Functions. Bell, London, 1895, p. 56.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Programs

  • Magma
    [(9^n-8*n-1)/16: n in [0..25]]; // Vincenzo Librandi, Jun 29 2011
  • Mathematica
    a[ n_] := If[ n < 0, 0, (-1)^n (2 n)! Coefficient[ SeriesCoefficient[ JacobiCN[x, m], {x, 0, 2 n}], m, 1]]; (* Michael Somos, Dec 27 2014 *)
    LinearRecurrence[{11, -19, 9}, {0, 0, 4}, 21] (* Jean-François Alcover, Sep 21 2017 *)
  • PARI
    {a(n) = (9^n - 8*n -1) / 16}; /* Michael Somos, Jun 27 2003 */
    

Formula

From Michael Somos, Jun 27 2003: (Start)
G.f.: 4*x^2/((1-x)^2*(1-9*x)).
a(n) = (9^n-8*n-1)/16. (End)
a(n+2) = 4*A014832(n+1). [Bruno Berselli, Jun 29 2011]

Extensions

More terms from Paolo Dominici (pl.dm(AT)libero.it) using formulas 16.22.1 and 16.22.2 of Abramowitz and Stegun's Handbook of Mathematical Functions.

A014857 Numbers k that divide s(k), where s(1)=1, s(j)=9*s(j-1)+j.

Original entry on oeis.org

1, 3, 9, 21, 39, 63, 117, 147, 171, 273, 333, 441, 507, 819, 903, 1029, 1197, 1521, 1911, 2223, 2331, 2709, 3081, 3087, 3249, 3549, 4329, 5733, 6123, 6321, 6327, 6591, 6813, 7203, 8001, 8379, 9243, 10647, 11487, 11739, 12207, 12321, 13377
Offset: 1

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Author

Keywords

Crossrefs

s(n) = A014832(n).
Showing 1-4 of 4 results.