A175878 Odd terms in A007497.
3, 7, 15, 564210119465811
Offset: 1
Programs
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Mathematica
n=2;Do[If[OddQ[n=DivisorSigma[1,n]],Print[n]],{k,2,99}]
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.