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.

A051152 (-1)sigma sociable number of order 2: (-1)sigma((-1)sigma(x))=x, but (-1)sigma(x)<>x, where if x=Product p(i)^r(i) then (-1)sigma(x)=Product (-1+Sum p(i)^s(i), s(i)=1 to r(i)); (-1)sigma(1)=1.

Table of values

n a(n)
0 4
1 5
2 216
3 494
4 16800
5 21228
6 246400
7 440220

List of values

[4, 5, 216, 494, 16800, 21228, 246400, 440220]

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

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