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.

A257705 Sequence (a(n)) generated by Rule 1 (in Comments) with a(1) = 0 and d(1) = 0.

Original entry on oeis.org

0, 1, 3, 2, 5, 9, 7, 4, 10, 6, 11, 18, 13, 21, 15, 8, 17, 27, 19, 30, 20, 32, 23, 12, 25, 39, 26, 14, 29, 45, 31, 16, 33, 51, 35, 54, 37, 57, 38, 59, 41, 63, 43, 22, 46, 24, 47, 72, 49, 75, 50, 77, 53, 81, 55, 28, 58, 87, 56, 88, 60, 91, 62, 95, 65, 99, 67
Offset: 1

Views

Author

Clark Kimberling, May 12 2015

Keywords

Comments

Rule 1 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 greatest 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.
Conjecture: if a(1) is an nonnegative integer and d(1) is an integer, then (a(n)) is a permutation of the nonnegative integers (if a(1) = 0) or a permutation of the positive integers (if a(1) > 0). Moreover, (d(n)) is a permutation of the integers if d(1) = 0, or of the nonzero integers if d(1) > 0.
Guide to related sequences:
a(1) d(1) (a(n)) (d(n))
0 0 A257705 A131389 except for initial terms
0 1 A257706 A131389 except for initial terms
0 2 A257876 A131389 except for initial terms
1 1 A257878 A131389 except for initial terms
2 1 A257881 A257880 except for initial terms

Examples

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

Crossrefs

Programs

  • Mathematica
    a[1] = 0; d[1] = 0; k = 1; z = 10000; zz = 120;
    A[k_] := Table[a[i], {i, 1, k}]; diff[k_] := Table[d[i], {i, 1, k}];
    c[k_] := Complement[Range[-z, z], diff[k]];
    T[k_] := -a[k] + Complement[Range[z], A[k]];
    s[k_] := Intersection[Range[-a[k], -1], c[k], T[k]];
    Table[If[Length[s[k]] == 0, {h = Min[Intersection[c[k], T[k]]], a[k + 1] = a[k] + h, d[k + 1] = h, k = k + 1}, {h = Max[s[k]], a[k + 1] = a[k] + h, d[k + 1] = h, k = k + 1}], {i, 1, zz}];
    u = Table[a[k], {k, 1, zz}] (* A257705 *)
    Table[d[k], {k, 1, zz}]     (* A131389 *)

Formula

a(k+1) - a(k) = d(k+1) for k >= 1.
Also, a(k) = A131388(n)-1.

A257879 Sequence (a(n)) generated by Rule 1 (in Comments) with a(1) = 2 and d(1) = 0.

Original entry on oeis.org

2, 1, 3, 4, 7, 5, 9, 6, 11, 17, 13, 8, 15, 23, 16, 10, 19, 29, 21, 12, 24, 14, 25, 38, 27, 41, 28, 43, 31, 47, 33, 18, 35, 53, 37, 20, 39, 59, 40, 22, 44, 65, 45, 68, 46, 70, 49, 26, 51, 77, 52, 79, 55, 83, 57, 30, 60, 32, 61, 92, 63, 95, 64, 34, 67, 101, 69
Offset: 1

Views

Author

Clark Kimberling, May 12 2015

Keywords

Comments

Rule 1 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 greatest 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.
Conjecture: if a(1) is an nonnegative integer and d(1) is an integer, then (a(n)) is a permutation of the nonnegative integers (if a(1) = 0) or a permutation of the positive integers (if a(1) > 0). Moreover, (d(n)) is a permutation of the integers if d(1) = 0, or of the nonzero integers if d(1) > 0.
See A257705 for a guide to related sequences.

Examples

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

Crossrefs

Programs

  • Mathematica
    a[1] = 2; d[1] = 0; k = 1; z = 10000; zz = 120;
    A[k_] := Table[a[i], {i, 1, k}]; diff[k_] := Table[d[i], {i, 1, k}];
    c[k_] := Complement[Range[-z, z], diff[k]];
    T[k_] := -a[k] + Complement[Range[z], A[k]];
    s[k_] := Intersection[Range[-a[k], -1], c[k], T[k]];
    Table[If[Length[s[k]] == 0, {h = Min[Intersection[c[k], T[k]]], a[k + 1] = a[k] + h, d[k + 1] = h, k = k + 1}, {h = Max[s[k]], a[k + 1] = a[k] + h, d[k + 1] = h, k = k + 1}], {i, 1, zz}];
    u = Table[a[k], {k, 1, zz}]  (* A257879 *)
    Table[d[k], {k, 1, zz}]  (* A257880 *)

Formula

a(k+1) - a(k) = d(k+1) for k >= 1.

A257882 Sequence (a(n)) generated by Rule 1 (in Comments) with a(1) = 2 and d(1) = 2.

Original entry on oeis.org

2, 1, 4, 5, 3, 7, 12, 9, 15, 11, 6, 13, 21, 14, 8, 17, 27, 19, 10, 22, 33, 23, 36, 25, 39, 26, 41, 29, 45, 31, 16, 34, 18, 35, 54, 37, 57, 38, 20, 42, 63, 43, 66, 44, 68, 47, 24, 49, 75, 51, 78, 53, 81, 55, 28, 58, 30, 59, 90, 61, 93, 62, 32, 65, 99, 67, 102
Offset: 1

Views

Author

Clark Kimberling, May 13 2015

Keywords

Comments

Rule 1 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 greatest 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.
Conjecture: if a(1) is an nonnegative integer and d(1) is an integer, then (a(n)) is a permutation of the nonnegative integers (if a(1) = 0) or a permutation of the positive integers (if a(1) > 0). Moreover, (d(n)) is a permutation of the integers if d(1) = 0, or of the nonzero integers if d(1) > 0.
See A257705 for a guide to related sequences.

Examples

			a(1) = 2, d(1) = 2;
a(2) = 1, d(2) = -1;
a(3) = 4, d(3) = 3;
a(4) = 5, d(4) = 1.
		

Crossrefs

Programs

  • Mathematica
    a[1] = 2; d[1] = 2; k = 1; z = 10000; zz = 120;
    A[k_] := Table[a[i], {i, 1, k}]; diff[k_] := Table[d[i], {i, 1, k}];
    c[k_] := Complement[Range[-z, z], diff[k]];
    T[k_] := -a[k] + Complement[Range[z], A[k]];
    s[k_] := Intersection[Range[-a[k], -1], c[k], T[k]];
    Table[If[Length[s[k]] == 0, {h = Min[Intersection[c[k], T[k]]], a[k + 1] = a[k] + h, d[k + 1] = h, k = k + 1}, {h = Max[s[k]], a[k + 1] = a[k] + h, d[k + 1] = h, k = k + 1}], {i, 1, zz}];
    u = Table[a[k], {k, 1, zz}]  (* A257882 *)
    Table[d[k], {k, 1, zz}]  (* A257918 *)

Formula

a(k+1) - a(k) = d(k+1) for k >= 1.

A257881 Sequence (a(n)) generated by Rule 1 (in Comments) with a(1) = 2 and d(1) = 1.

Original entry on oeis.org

2, 1, 3, 6, 4, 8, 5, 10, 16, 12, 7, 14, 22, 15, 9, 18, 28, 20, 11, 23, 13, 24, 37, 26, 40, 27, 42, 30, 46, 32, 17, 34, 52, 36, 19, 38, 58, 39, 21, 43, 64, 44, 67, 45, 69, 48, 25, 50, 76, 51, 78, 54, 82, 56, 29, 59, 31, 60, 91, 62, 94, 63, 33, 66, 100, 68, 35
Offset: 1

Views

Author

Clark Kimberling, May 13 2015

Keywords

Comments

Rule 1 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 greatest 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.
Conjecture: if a(1) is an nonnegative integer and d(1) is an integer, then (a(n)) is a permutation of the nonnegative integers (if a(1) = 0) or a permutation of the positive integers (if a(1) > 0). Moreover, (d(n)) is a permutation of the integers if d(1) = 0, or of the nonzero integers if d(1) > 0.
See A257705 for a guide to related sequences.

Examples

			a(1) = 2, d(1) = 0;
a(2) = 1, d(2) = -1;
a(3) = 3, d(3) = 2;
a(4) = 6, d(4) = 3.
		

Crossrefs

Programs

  • Mathematica
    a[1] = 2; d[1] = 1; k = 1; z = 10000; zz = 120;
    A[k_] := Table[a[i], {i, 1, k}]; diff[k_] := Table[d[i], {i, 1, k}];
    c[k_] := Complement[Range[-z, z], diff[k]];
    T[k_] := -a[k] + Complement[Range[z], A[k]];
    s[k_] := Intersection[Range[-a[k], -1], c[k], T[k]];
    Table[If[Length[s[k]] == 0, {h = Min[Intersection[c[k], T[k]]], a[k + 1] = a[k] + h, d[k + 1] = h, k = k + 1}, {h = Max[s[k]], a[k + 1] = a[k] + h, d[k + 1] = h, k = k + 1}], {i, 1, zz}];
    u = Table[a[k], {k, 1, zz}]  (* A257881 *)
    Table[d[k], {k, 1, zz}]  (* essentially A257880 *)

Formula

a(k+1) - a(k) = d(k+1) for k >= 1.
Showing 1-4 of 4 results.