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.

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A230455 Lexicographically earliest sequence of distinct positive integers such that the absolute value of the first difference contains only distinct squares.

Original entry on oeis.org

1, 2, 6, 15, 31, 56, 7, 43, 107, 26, 126, 5, 149, 318, 29, 225, 450, 9, 265, 589, 13, 374, 774, 45, 529, 1058, 34, 659, 1335, 39, 823, 1664, 64, 964, 3, 1092, 2248, 132, 1357, 2726, 22, 1466, 2987, 71, 1752, 3516, 35, 1884, 3820, 99, 2124, 4333, 108, 2412
Offset: 1

Views

Author

Paul Tek, Oct 19 2013

Keywords

Comments

Is this a permutation of the positive integers ?
Will every square show up in the absolute value of the first difference ?

Examples

			The first differences of 1, 2, 6, 15, 31,... are 1^2, 2^2, 3^2, 4^2, 5^2, 7^2, 6^2,...
		

Crossrefs

Programs

  • Perl
    See Link section.

A257877 Sequence (a(n)) generated by Rule 1 (in Comments) with a(1) = 0 and d(1) = 3.

Original entry on oeis.org

0, 1, 3, 2, 6, 4, 9, 5, 11, 8, 15, 10, 18, 12, 21, 14, 24, 16, 7, 19, 30, 20, 33, 22, 36, 23, 38, 26, 42, 28, 13, 31, 48, 32, 51, 34, 54, 35, 17, 39, 60, 40, 63, 41, 65, 44, 69, 46, 72, 47, 74, 50, 78, 52, 25, 55, 27, 56, 87, 58, 90, 59, 29, 62, 96, 64, 99
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) = 0, d(1) = 3;
a(2) = 1, d(2) = 1;
a(3) = 3, d(3) = 2;
a(4) = 2, d(4) = -1.
		

Crossrefs

Programs

  • Mathematica
    a[1] = 0; d[1] = 3; 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}]  (* A257877 *)
    Table[d[k], {k, 1, zz}]  (* A257915 *)

Formula

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

A230383 Lexicographically earliest sequence of distinct positive integers such that the first difference contains only distinct positive or negative squares.

Original entry on oeis.org

1, 2, 6, 5, 14, 10, 26, 17, 42, 78, 29, 4, 53, 37, 101, 20, 120, 56, 137, 16, 160, 60, 24, 145, 314, 25, 221, 52, 277, 21, 310, 85, 341, 197, 521, 80, 441, 41, 482, 121, 605, 76, 476, 152, 681, 105, 730, 54, 630, 146, 822, 38, 767, 142, 926, 1767, 3, 903, 62
Offset: 1

Views

Author

Paul Tek, Oct 17 2013

Keywords

Comments

Is this a permutation of the positive integers ?
Will every square show up in the first difference ?

Examples

			n  a(n)   First difference
-  ----   ----------------
1     1
          +1^2
2     2
          +2^2
3     6
          -1^2
4     5
          +3^2
5    14
          -2^2
6    10
          +4^2
7    26
          ...
		

Crossrefs

Programs

  • Perl
    See Link section.

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.

A257884 Sequence (a(n)) generated by Algorithm (in Comments) with a(1) = 0 and d(1) = 1.

Original entry on oeis.org

0, 2, 1, 4, 8, 3, 9, 5, 10, 7, 14, 6, 15, 13, 21, 11, 22, 16, 26, 12, 24, 17, 30, 18, 32, 19, 34, 23, 39, 20, 37, 28, 46, 25, 44, 27, 47, 29, 50, 35, 57, 31, 54, 38, 62, 33, 58, 36, 63, 40, 66, 41, 69, 42, 71, 43, 73, 49, 80, 45, 77, 110, 48, 82, 51, 86, 52
Offset: 1

Views

Author

Clark Kimberling, May 13 2015

Keywords

Comments

Algorithm: 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). Let h be the least integer > -a(k) such that h is not in D(k) and 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 repeat inductively.
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 A257883 for a guide to related sequences.

Examples

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

Crossrefs

Programs

  • Mathematica
    a[1] = 0; 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]]
    Table[{h = Min[Intersection[c[k], T[k]]], a[k + 1] = a[k] + h,
       d[k + 1] = h, k = k + 1}, {i, 1, zz}];
    u = Table[a[k], {k, 1, zz}]  (* A257884 *)
    Table[d[k], {k, 1, zz}]      (* A175499 *)

Formula

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

A257876 Sequence (a(n)) generated by Rule 1 (in Comments) with a(1) = 0 and d(1) = 2.

Original entry on oeis.org

0, 1, 4, 3, 7, 5, 2, 8, 13, 9, 16, 11, 19, 12, 6, 15, 25, 17, 28, 18, 30, 21, 10, 23, 37, 24, 39, 27, 43, 29, 14, 31, 49, 33, 52, 35, 55, 36, 57, 34, 56, 38, 61, 41, 20, 44, 22, 47, 73, 48, 75, 51, 79, 53, 26, 58, 87, 59, 89, 60, 91, 54, 88, 50, 83, 42, 77
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) = 0, d(1) = 2;
a(2) = 1, d(2) = 1;
a(3) = 3, d(3) = 3;
a(4) = 4, d(4) = -1.
The first terms of (d(n)) are (2,1,3,-1,4,-2,-3,6,5,...), which differs from A131389 only in initial terms.
		

Crossrefs

Programs

  • Mathematica
    a[1] = 0; 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}]  (* A257876 *)
    Table[d[k], {k, 1, zz}]      (* A131389 essentially *)

Formula

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

A257878 Sequence (a(n)) generated by Rule 1 (in Comments) with a(1) = 1 and d(1) = 1.

Original entry on oeis.org

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, 34
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.
Considering the first 1000 elements of this sequence and A257705 it appears that this is the same as A257705 apart from an index shift. - R. J. Mathar, May 14 2015

Examples

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

Crossrefs

Programs

  • Mathematica
    a[1] = 1; 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}]  (* A257878 *)
    Table[d[k], {k, 1, zz}]      (* A131389 essentially *)

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.

A327844 Table read by antidiagonals: the m-th row gives the sequence constructed by repeatedly choosing the smallest positive number not already in the row such that for each k = 1, ..., m, the k-th differences are distinct.

Original entry on oeis.org

1, 1, 2, 1, 2, 4, 1, 2, 4, 3, 1, 2, 4, 3, 6, 1, 2, 4, 3, 6, 10, 1, 2, 4, 3, 6, 11, 5, 1, 2, 4, 3, 6, 11, 5, 11, 1, 2, 4, 3, 6, 11, 5, 9, 7, 1, 2, 4, 3, 6, 11, 5, 9, 7, 12, 1, 2, 4, 3, 6, 11, 5, 9, 7, 13, 9, 1, 2, 4, 3, 6, 11, 5, 9, 7, 13, 10, 16, 1, 2, 4, 3
Offset: 1

Views

Author

Peter Kagey, Sep 29 2019

Keywords

Comments

First row is A175498. Main diagonal is A327743.
The index of where the m-th row first differs from A327743 is 6, 15, 15, 16, 16, 194, 301, 301, 1036, 1036, 1036, 1037, ...
For example, T(6, 194) != A327743(194), but T(6, n) = A327743(n) for n < 194.

Examples

			Table begins:
1, 2, 4, 3, 6, 10, 5, 11, 7, 12,  9, 16, 8, 17, 15, 23, ...
1, 2, 4, 3, 6, 11, 5,  9, 7, 13, 10, 18, 8, 15, 25, 12, ...
1, 2, 4, 3, 6, 11, 5,  9, 7, 13, 10, 18, 8, 15, 25, 12, ...
1, 2, 4, 3, 6, 11, 5,  9, 7, 13, 10, 18, 8, 15, 27, 12, ...
1, 2, 4, 3, 6, 11, 5,  9, 7, 13, 10, 18, 8, 15, 27, 12, ...
1, 2, 4, 3, 6, 11, 5,  9, 7, 13, 10, 18, 8, 15, 27, 14, ...
		

Crossrefs

Previous Showing 11-20 of 21 results. Next