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 1-5 of 5 results.

A026438 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1 <= i <= j < n, n >= 2, with initial terms 1,3.

Original entry on oeis.org

1, 3, 4, 5, 6, 7, 9, 10, 12, 13, 16, 18, 21, 22, 25, 28, 30, 31, 32, 33, 36, 37, 40, 42, 43, 45, 46, 50, 52, 54, 55, 56, 57, 58, 60, 61, 66, 67, 68, 70, 72, 73, 75, 76, 78, 81, 82, 84, 85, 86, 88, 91, 93, 94, 96, 97, 100, 101, 102, 103
Offset: 1

Views

Author

Clark Kimberling

Keywords

Links

Crossrefs

Cf. A026437 and references therein.

Programs

  • Mathematica
    a = {1, 3}; used = Flatten@Outer[Times, a, a] - 1; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; AppendTo[a, k]; used = Union[used, k*a - 1], {n, 3, 60}]; a (* Ivan Neretin, Feb 15 2018 *)

Extensions

Name clarified by Robert C. Lyons, Feb 06 2025

A026439 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1 <= i <= j < n, n >= 2, with initial terms 2,3.

Original entry on oeis.org

2, 3, 4, 6, 9, 10, 12, 13, 14, 16, 18, 20, 21, 22, 24, 28, 30, 32, 33, 34, 36, 37, 40, 42, 44, 45, 46, 48, 49, 50, 52, 54, 56, 57, 58, 60, 61, 64, 66, 68, 69, 70, 72, 74, 75, 76, 78, 81, 82, 84, 85, 86, 88, 90, 92, 93, 94, 96, 100, 102
Offset: 1

Views

Author

Clark Kimberling

Keywords

Links

Crossrefs

Cf. A026437 and references therein.

Programs

  • Mathematica
    a = {2, 3}; used = Flatten@Outer[Times, a, a] - 1; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; AppendTo[a, k]; used = Union[used, k*a - 1], {n, 3, 60}]; a (* Ivan Neretin, Feb 15 2018 *)

Extensions

Name clarified by Robert C. Lyons, Feb 06 2025

A026440 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1 <= i <= j < n, n >= 2, with initial terms 1,4.

Original entry on oeis.org

1, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 16, 17, 18, 20, 21, 22, 25, 26, 28, 30, 32, 33, 36, 37, 38, 40, 42, 45, 46, 50, 52, 56, 57, 58, 60, 61, 66, 68, 70, 72, 73, 74, 75, 78, 81, 82, 85, 86, 88, 91, 92, 93, 94, 96, 100, 102, 105, 106
Offset: 1

Views

Author

Clark Kimberling

Keywords

Links

Crossrefs

Cf. A026437 and references therein.

Programs

  • Mathematica
    a = {1, 4}; used = Flatten@Outer[Times, a, a] - 1; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; AppendTo[a, k]; used = Union[used, k*a - 1], {n, 3, 60}]; a (* Ivan Neretin, Feb 15 2018 *)

Extensions

Name clarified by Robert C. Lyons, Feb 06 2025

A026441 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1 <= i <= j < n, n >= 2, with initial terms 2,4.

Original entry on oeis.org

2, 4, 5, 6, 8, 10, 12, 13, 14, 16, 17, 18, 20, 21, 22, 26, 28, 30, 32, 34, 36, 37, 38, 40, 42, 44, 45, 46, 48, 50, 52, 53, 54, 56, 57, 58, 60, 61, 62, 65, 66, 68, 70, 72, 74, 76, 78, 80, 81, 82, 85, 86, 88, 90, 92, 93, 94, 96, 97, 98
Offset: 1

Views

Author

Clark Kimberling

Keywords

Comments

Appears to be A026437 shifted once left. - R. J. Mathar, Jul 13 2025

Links

Crossrefs

Cf. A026437 and references therein.

Programs

  • Mathematica
    a = {2, 4}; used = Flatten@Outer[Times, a, a] - 1; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; AppendTo[a, k]; used = Union[used, k*a - 1], {n, 3, 60}]; a (* Ivan Neretin, Feb 15 2018 *)

Extensions

Name clarified by Robert C. Lyons, Feb 06 2025

A026442 a(n) = least positive integer > a(n-1) and not a(i)*a(j)-1 for 1 <= i <= j < n, n >= 2, with initial terms 3,4.

Original entry on oeis.org

3, 4, 5, 6, 7, 9, 10, 12, 13, 16, 18, 21, 22, 25, 28, 30, 31, 32, 33, 36, 37, 40, 42, 43, 45, 46, 50, 52, 54, 55, 56, 57, 58, 60, 61, 66, 67, 68, 70, 72, 73, 75, 76, 78, 81, 82, 84, 85, 86, 88, 91, 93, 94, 96, 97, 100, 101, 102, 103, 105
Offset: 1

Views

Author

Clark Kimberling

Keywords

Comments

a(n) = A026438(n+1) for n > 1. - Georg Fischer, Oct 22 2018

Links

Crossrefs

Cf. A026437 and references therein.
Cf. A026438.

Programs

  • Mathematica
    a = {3, 4}; used = Flatten@Outer[Times, a, a] - 1; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; AppendTo[a, k]; used = Union[used, k*a - 1], {n, 3, 60}]; a (* Ivan Neretin, Feb 15 2018 *)

Extensions

Name clarified by Robert C. Lyons, Feb 06 2025
Showing 1-5 of 5 results.

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