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

0, 1, 1045, 5985, 123395663059845, 774611255177760

Offset: 1

Author

Seiichi Manyama, May 16 2021

Keywords

• nonn
• fini
• full

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