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.

A258047 Sequence (d(n)) generated by Rule 3 (in Comments) with a(1) = 1 and d(1) = 0.

Original entry on oeis.org

0, 1, 2, -1, 3, 6, -7, 5, -3, 7, -6, 8, -5, -2, 9, 18, -23, 13, -11, 15, -13, 17, -15, 19, -18, 20, -19, 21, -20, 22, -21, 23, -22, 24, -17, -4, 27, -29, 25, -9, -12, 29, -30, 28, -24, 32, -31, 33, -27, 4, -8, 35, -33, 37, -25, 49, -53, 45, -43, 47, -42, 52
Offset: 1

Views

Author

Clark Kimberling, Jun 05 2015

Keywords

Comments

Rule 3 follows. For k >= 1, let A(k) = {a(1), …, a(k)} and D(k) = {d(1), …, d(k)}. Begin with k = 1 and nonnegative integers a(1) and d(1).
Step 1: If there is an integer h such that 1 - a(k) < h < 0 and h is not in D(k) and a(k) + h is not in A(k), let d(k+1) be the least such h, let a(k+1) = a(k) + h, replace k by k + 1, and repeat Step 1; otherwise do Step 2.
Step 2: Let h be the least positive integer not in D(k) such that a(k) - h is not in A(k). Let a(k+1) = a(k) + h and d(k+1) = h. Replace k by k+1 and do Step 1.
See A257905 for a guide to related sequences and conjectures.

Examples

			a(1) = 1, d(1) = 0;
a(2) = 2, d(2) = 1;
a(3) = 4, d(3) = 2;
a(4) = 3, d(4) = -1.
		

Crossrefs

Programs

  • Mathematica
    {a, f} = {{1}, {0}}; Do[tmp = {#, # - Last[a]} &[Min[Complement[#, Intersection[a, #]]&[Last[a] + Complement[#, Intersection[f, #]] &[Range[2 - Last[a], -1]]]]];
    If[! IntegerQ[tmp[[1]]], tmp = {Last[a] + #, #} &[NestWhile[# + 1 &, 1, ! (! MemberQ[f, #] && ! MemberQ[a, Last[a] - #]) &]]]; AppendTo[a, tmp[[1]]]; AppendTo[f, tmp[[2]]], {120}]; {a, f} (* Peter J. C. Moses, May 14 2015 *)

A258050 Position of -n in A258047 after deleting the initial 0.

Original entry on oeis.org

3, 6, 8, 10, 12, 13, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 35, 37, 39, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110, 112, 114, 116, 118, 120, 122, 124
Offset: 1

Views

Author

Clark Kimberling, Jun 05 2015

Keywords

Comments

A258047 = (0,1,2,-1,3,6,-7,5,-3,7,...). Remove the initial 0 to get (1,2,-1,3,6,-7,5,6,-3,7,...), and note that (1,2,3,4,...) occupy positions 1,2,4,7,..., (as in A258049) and that (-1,-2,-3,...) occupy positions 3,6,8,... (as in A258050).

Crossrefs

Cf. A258047, A258049 (complement).

Programs

  • Mathematica
    {a, f} = {{1}, {0}}; Do[tmp = {#, # - Last[a]} &[Min[Complement[#, Intersection[a, #]]&[Last[a] + Complement[#, Intersection[f, #]] &[Range[2 - Last[a], -1]]]]];
    If[! IntegerQ[tmp[[1]]], tmp = {Last[a] + #, #} &[NestWhile[# + 1 &, 1, ! (! MemberQ[f, #] && ! MemberQ[a, Last[a] - #]) &]]];
    AppendTo[a, tmp[[1]]]; AppendTo[f, tmp[[2]]], {500}];
    -1 + Flatten[Position[Sign[f], 1]]  (* A258049 *)
    -1 + Flatten[Position[Sign[f], -1]] (* A258050 *) (* Peter J. C. Moses, May 14 2015 *)

A258046 Sequence (a(n)) generated by Rule 3 (in Comments) with a(1) = 1 and d(1) = 0.

Original entry on oeis.org

1, 2, 4, 3, 6, 12, 5, 10, 7, 14, 8, 16, 11, 9, 18, 36, 13, 26, 15, 30, 17, 34, 19, 38, 20, 40, 21, 42, 22, 44, 23, 46, 24, 48, 31, 27, 54, 25, 50, 41, 29, 58, 28, 56, 32, 64, 33, 66, 39, 43, 35, 70, 37, 74, 49, 98, 45, 90, 47, 94, 52, 104, 53, 106, 51, 102
Offset: 1

Views

Author

Clark Kimberling, Jun 03 2015

Keywords

Comments

Rule 3 follows. For k >= 1, let A(k) = {a(1), …, a(k)} and D(k) = {d(1), …, d(k)}. Begin with k = 1 and nonnegative integers a(1) and d(1).
Step 1: If there is an integer h such that 1 - a(k) < h < 0 and h is not in D(k) and a(k) + h is not in A(k), let d(k+1) be the least such h, let a(k+1) = a(k) + h, replace k by k + 1, and repeat Step 1; otherwise do Step 2.
Step 2: Let h be the least positive integer not in D(k) such that a(k) - h is not in A(k). Let a(k+1) = a(k) + h and d(k+1) = h. Replace k by k+1 and do Step 1.
See A257905 for a guide to related sequences and conjectures.

Examples

			a(1) = 1, d(1) = 0;
a(2) = 2, d(2) = 1;
a(3) = 4, d(3) = 2;
a(4) = 3, d(4) = -1.
		

Crossrefs

Programs

  • Mathematica
    {a, f} = {{1}, {0}}; Do[tmp = {#, # - Last[a]} &[Min[Complement[#, Intersection[a, #]]&[Last[a] + Complement[#, Intersection[f, #]] &[Range[2 - Last[a], -1]]]]];
    If[! IntegerQ[tmp[[1]]], tmp = {Last[a] + #, #} &[NestWhile[# + 1 &, 1, ! (! MemberQ[f, #] && ! MemberQ[a, Last[a] - #]) &]]]; AppendTo[a, tmp[[1]]]; AppendTo[f, tmp[[2]]], {120}]; {a, f} (* Peter J. C. Moses, May 14 2015 *)
Showing 1-3 of 3 results.