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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.

A253920 Indices of centered octagonal numbers (A016754) which are also heptagonal numbers (A000566).

Table of values

n a(n)
1 1
2 5
3 39
4 760
5 6494
6 55518
7 1095199
8 9363623
9 80056197
10 1579275478
11 13502337152
12 115440979836
13 2277314143357
14 19470360808841
15 166465812866595
16 3283885415444596
17 28076246784010850
18 240043586712649434
19 4735360491756963355
20 40485928392182836139

List of values

[1, 5, 39, 760, 6494, 55518, 1095199, 9363623, 80056197, 1579275478, 13502337152, 115440979836, 2277314143357, 19470360808841, 166465812866595, 3283885415444596, 28076246784010850, 240043586712649434, 4735360491756963355, 40485928392182836139]

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

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