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.

A194105 Inverse permutation of A194104; every positive integer occurs exactly once.

Original entry on oeis.org

1, 3, 2, 5, 6, 10, 4, 8, 9, 14, 15, 7, 12, 13, 19, 20, 21, 28, 11, 17, 18, 25, 26, 27, 35, 36, 16, 23, 24, 32, 33, 34, 43, 44, 45, 22, 30, 31, 40, 41, 42, 52, 53, 54, 55, 66, 29, 38, 39, 49, 50, 51, 62, 63, 64, 65, 77, 78, 37, 47, 48, 59, 60, 61, 73, 74, 75, 76, 89
Offset: 1

Views

Author

Clark Kimberling, Aug 15 2011

Keywords

Crossrefs

Cf. A194104.

Programs

A194102 a(n) = Sum_{j=1..n} floor(j*sqrt(2)); n-th partial sum of Beatty sequence for sqrt(2), A001951.

Original entry on oeis.org

1, 3, 7, 12, 19, 27, 36, 47, 59, 73, 88, 104, 122, 141, 162, 184, 208, 233, 259, 287, 316, 347, 379, 412, 447, 483, 521, 560, 601, 643, 686, 731, 777, 825, 874, 924, 976, 1029, 1084, 1140, 1197, 1256, 1316, 1378, 1441, 1506, 1572, 1639, 1708, 1778
Offset: 1

Views

Author

Clark Kimberling, Aug 15 2011

Keywords

Comments

The natural fractal sequence of A194102 is A194103; the natural interspersion is A194104. See A194029 for definitions.

Crossrefs

Programs

  • Magma
    [(&+[Floor(k*Sqrt(2)): k in [1..n]]): n in [1..100]]; // G. C. Greubel, Jun 05 2018
  • Mathematica
    a[n_]:=Sum[Floor[j*Sqrt[2]], {j, 1, n}]; Table[a[n], {n, 1, 90}]
  • PARI
    apply( A194102(n)=sum(k=1,n,sqrtint(k^2*2)), [1..99]) \\ M. F. Hasler, Jan 16 2021
    
  • PARI
    apply( {A194102(n)=if(n>1, (1+n=sqrtint(n^2*2))*n\2-A194102(n-=sqrtint(n^2\2)+1)-(1+n)*n, n)}, [1..99]) \\ M. F. Hasler, Apr 23 2022
    

Formula

a(n) = B*(B+1)/2 - C*(C+1) - a(C) where B = floor(sqrt(2)*n) and C = floor(B/(sqrt(2)+2)). - M. F. Hasler, Apr 23 2022

A194103 Natural fractal sequence of A194102.

Original entry on oeis.org

1, 2, 1, 2, 3, 4, 1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 6, 7, 1, 2, 3, 4, 5, 6, 7, 8, 1, 2, 3, 4, 5, 6, 7, 8, 9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 1, 2, 3, 4
Offset: 1

Views

Author

Clark Kimberling, Aug 15 2011

Keywords

Comments

See A194029 for definitions of natural fractal sequence and natural interspersion.

Crossrefs

Programs

  • Mathematica
    z = 40; g = Sqrt[2];
    c[k_] := Sum[Floor[j*g], {j, 1, k}];
    c = Table[c[k], {k, 1, z}]  (* A194102 *)
    f[n_] := If[MemberQ[c, n], 1, 1 + f[n - 1]]
    f = Table[f[n], {n, 1, 800}]  (* A194103  new *)
    r[n_] := Flatten[Position[f, n]]
    t[n_, k_] := r[n][[k]]
    TableForm[Table[t[n, k], {n, 1, 8}, {k, 1, 7}]]
    p = Flatten[Table[t[k, n - k + 1], {n, 1, 16}, {k, 1, n}]]  (* A194104 *)
    q[n_] := Position[p, n]; Flatten[Table[q[n], {n, 1, 80}]]  (* A194105 *)
Showing 1-3 of 3 results.