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.

A257472 Inverse permutation to A257471.

Original entry on oeis.org

1, 2, 3, 4, 6, 5, 11, 7, 8, 9, 22, 10, 30, 14, 12, 13, 49, 15, 59, 16, 17, 27, 84, 18, 19, 35, 23, 20, 125, 21, 142, 24, 31, 54, 25, 26, 195, 66, 40, 28, 233, 29, 255, 36, 32, 92, 302, 33, 34, 37, 60, 45, 377, 38, 41, 39, 72, 135, 459, 42, 486, 151, 43, 44, 50, 46, 580, 67
Offset: 1

Views

Author

Ivan Neretin, Apr 25 2015

Keywords

Links

Crossrefs

Cf. A003991 (multiplication table), A257471 (inverse permutation).

A374797 Distinct value of A003990 (LCM table read by antidiagonals) in order of appearance.

Original entry on oeis.org

1, 2, 3, 4, 6, 5, 10, 12, 7, 15, 8, 14, 20, 9, 21, 18, 24, 28, 30, 11, 35, 22, 36, 40, 42, 13, 33, 45, 26, 44, 56, 39, 55, 63, 16, 52, 60, 66, 70, 72, 17, 65, 77, 34, 48, 78, 84, 88, 90, 19, 51, 91, 99, 38, 68, 80, 104, 110, 57, 85, 105, 117, 76, 102, 112, 120
Offset: 1

Views

Author

Rémy Sigrist, Jul 20 2024

Keywords

Comments

This sequence is a permutation of the positive integers with inverse A374798 and similar to A257471.

Examples

			The first terms of A003990 are: 1, 2, 2, 3, 2, 3, 4, 6, 6, 4, 5, 4, 3, 4, 5, 6, 10. Removing duplicates yields 1, 2, 3, 4, 6, 5, 10.

Links

Crossrefs

Cf. A003990, A257471 (analog for multiplication table), A374798 (inverse).

Programs

  • PARI
    \\ See Links section.

A355170 The composite numbers in order of appearance in A173395.

Original entry on oeis.org

4, 6, 8, 9, 10, 12, 15, 16, 14, 18, 20, 21, 24, 25, 28, 30, 27, 32, 35, 36, 22, 40, 42, 33, 45, 48, 49, 26, 44, 50, 54, 56, 39, 55, 60, 63, 64, 52, 66, 70, 72, 65, 77, 80, 81, 34, 78, 84, 88, 90, 51, 75, 91, 96, 99, 100, 38, 68, 98, 104, 108, 110, 57, 85, 105
Offset: 1

Views

Author

Denver Massey, Jun 22 2022

Keywords

Comments

This sequence can be generated by removing duplicates from A173395. As such, every number in this sequence is composite, and every composite number appears in this sequence.
This gives a method of enumerating the composite numbers.

Examples

			This sequence can be generated by reading along the diagonals of the multiplication table with headers starting at 2, skipping any number that has already been seen:
   4  6  8 10 12 ...
   6  9 12 15 18 ...
   8 12 16 20 24 ...
  10 15 20 25 30 ...
  12 18 24 30 36 ...
  ...

Crossrefs

Cf. A173395, A257471 (similar construction).
Showing 1-3 of 3 results.

Started in 1964 by Neil J. A. Sloane | Maintained by The OEIS Foundation Inc.

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