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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.

A259937 Concatenation of the numbers from 1 to n with numbers from n down to 1.

Table of values

n a(n)
1 11
2 1221
3 123321
4 12344321
5 1234554321
6 123456654321
7 12345677654321
8 1234567887654321
9 123456789987654321
10 1234567891010987654321
11 12345678910111110987654321
12 123456789101112121110987654321

List of values

[11, 1221, 123321, 12344321, 1234554321, 123456654321, 12345677654321, 1234567887654321, 123456789987654321, 1234567891010987654321, 12345678910111110987654321, 123456789101112121110987654321]

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

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