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.

A158772 a(n) = A138635(n+18)-A138635(n).

Original entry on oeis.org

21, 21, 21, 42, 42, 42, 84, 84, 84, 168, 168, 168, 336, 336, 336, 672, 672, 672, 1344, 1344, 1344, 2688, 2688, 2688, 5376, 5376, 5376, 10752, 10752, 10752, 21504, 21504, 21504, 43008, 43008, 43008, 86016, 86016, 86016, 172032, 172032, 172032, 344064
Offset: 0

Views

Author

Paul Curtz, Mar 26 2009

Keywords

Comments

a(n) divided by 21 is the sequence 1,1,1,2,2,2,4,4,4,.., that is A000079 triplicated.

Extensions

Edited by R. J. Mathar, May 17 2009

A158780 a(2n) = A131577(n), a(2n+1) = A011782(n).

Original entry on oeis.org

0, 1, 1, 1, 2, 2, 4, 4, 8, 8, 16, 16, 32, 32, 64, 64, 128, 128, 256, 256, 512, 512, 1024, 1024, 2048, 2048, 4096, 4096, 8192, 8192, 16384, 16384, 32768, 32768, 65536, 65536, 131072, 131072, 262144, 262144, 524288, 524288, 1048576, 1048576, 2097152, 2097152, 4194304
Offset: 0

Views

Author

Paul Curtz, Mar 26 2009

Keywords

Comments

This construction combines the 2 basic sequences which equal their first differences in the same way as A138635 does for sequences which equal their 3rd differences and A137171 does for sequences which equal their fourth differences.
Essentially the same as A016116, A060546, and A131572. - R. J. Mathar, Apr 08 2009
Dropping a(0), this is the inverse binomial transform of A024537. - R. J. Mathar, Apr 08 2009

Links

Crossrefs

The following sequences are all essentially the same, in the sense that they are simple transformations of each other, with A029744 = {s(n), n>=1}, the numbers 2^k and 3*2^k, as the parent: A029744 (s(n)); A052955 (s(n)-1), A027383 (s(n)-2), A354788 (s(n)-3), A347789 (s(n)-4), A209721 (s(n)+1), A209722 (s(n)+2), A343177 (s(n)+3), A209723 (s(n)+4); A060482, A136252 (minor differences from A354788 at the start); A354785 (3*s(n)), A354789 (3*s(n)-7). The first differences of A029744 are 1,1,1,2,2,4,4,8,8,... which essentially matches eight sequences: A016116, A060546, A117575, A131572, A152166, A158780, A163403, A320770. The bisections of A029744 are A000079 and A007283. - N. J. A. Sloane, Jul 14 2022

Programs

  • Magma
    [0,1] cat [2^Floor((n-2)/2): n in [2..50]]; // G. C. Greubel, Apr 19 2023
  • Mathematica
    Table[(2^Floor[n/2] +Boole[n==1] -Boole[n==0])/2, {n,0,50}] (* or *) LinearRecurrence[{0,2}, {0,1,1,1}, 51] (* G. C. Greubel, Apr 19 2023 *)
  • PARI
    a(n)=if(n>3,([0,1; 2,0]^n*[1;1])[1,1]/2,n>0) \\ Charles R Greathouse IV, Oct 18 2022
  • SageMath
    def A158780(n): return (2^(n//2) + int(n==1) - int(n==0))/2
[A158780(n) for n in range(51)] # G. C. Greubel, Apr 19 2023

Formula

a(2n) + a(2n+1) = A000079(n).
G.f.: x*(1+x-x^2)/(1-2*x^2). - R. J. Mathar, Apr 08 2009
a(n) = (1/2)*(2^floor(n/2) + [n=1] - [n=0]). - G. C. Greubel, Apr 19 2023
E.g.f.: (2*cosh(sqrt(2)*x) + sqrt(2)*sinh(sqrt(2)*x) + 2*x - 2)/4. - Stefano Spezia, May 13 2023

Extensions

Edited by R. J. Mathar, Apr 08 2009

A158745 a(3n)=A130750(n). a(3n+1)=A130752(n). a(3n+2)=A130755(n).

Original entry on oeis.org

1, 2, 3, 3, 5, 4, 8, 9, 7, 17, 16, 15, 33, 31, 32, 64, 63, 65, 127, 128, 129, 255, 257, 256, 512, 513, 511, 1025, 1024, 1023, 2049, 2047, 2048, 4096, 4095, 4097, 8191, 8192, 8193, 16383, 16385, 16384, 32768, 32769, 32767, 65537, 65536, 65535, 131073, 131071, 131072, 262144
Offset: 0

Views

Author

Paul Curtz, Mar 25 2009

Keywords

Comments

This mixes three sequences which are identical to their third differences.

Links

Crossrefs

Cf. A138635, A140430, A130785, A140495.

Programs

  • Mathematica
    LinearRecurrence[{0,0,3,0,0,-3,0,0,2},{1,2,3,3,5,4,8,9,7},60] (* Harvey P. Dale, Mar 12 2023 *)

Formula

a(3n)+a(3n+1)+a(3n+2)= A007283(n+1).
a(18n) = A130750(6n)= 2^(6n+1)-1.
a(n) = 3*a(n-3)-3*a(n-6)+2*a(n-9). G.f.: -(1+2*x+3*x^2-x^4-5*x^5+2*x^6+4*x^8)/((2*x^3-1)*(x^6-x^3+1)). - R. J. Mathar, Jan 23 2009

Extensions

Edited and extended by R. J. Mathar, Apr 09 2009
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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