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 1-2 of 2 results.

A344376 Numbers that are both octagonal numbers (A000567) and octagonal pyramidal numbers (A002414).

Original entry on oeis.org

0, 1, 1045, 5985, 123395663059845, 774611255177760
Offset: 1

Views

Author

Seiichi Manyama, May 16 2021

Keywords

Comments

Terms correspond to integral points on an elliptic curve, which allows all of them to be found efficiently. - Max Alekseyev, Feb 19 2024

Crossrefs

Intersection of A000567 and A002414.
Cf. A027568, A334012.
Cf. A378361 (octagonal indices), A378918 (octagonal pyramidal indices).

Programs

  • PARI
    for(k=0, 1e5, if(ispolygonal(m=k*(k+1)*(2*k-1)/2, 8), print1(m", ")))

Extensions

Keywords 'fini' and 'full' added by Max Alekseyev, Feb 19 2024

A378918 Indices of octagonal pyramidal numbers that are both octagonal and octagonal pyramidal.

Original entry on oeis.org

0, 1, 10, 18, 49785, 91839
Offset: 1

Views

Author

Kelvin Voskuijl, Dec 10 2024

Keywords

Examples

			10 is a term because the 10th octagonal pyramidal number (1045) is also the 19th octagonal number.

Crossrefs

Cf. A000567 (octagonal numbers), A002414 (octagonal pyramidal numbers).
Cf. A344376.
Cf. A378361 (octagonal indices).

Formula

A344376(n) = A002414(a(n)).
Showing 1-2 of 2 results.

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

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