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.

A193072 Odd numbers N for which numerator(sigma(N^2)/N^2) is prime but sigma(N^2) is composite.

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%I A193072 #21 Oct 10 2022 07:57:04
%S A193072 39,507,2379,6591,13167,29511,148955,1672209,8852259,212370543,
%T A193072 1929229929
%N A193072 Odd numbers N for which numerator(sigma(N^2)/N^2) is prime but sigma(N^2) is composite.
%C A193072 a(12) > 10^10. - _Lucas A. Brown_, Apr 12 2021
%H A193072 Lucas A. Brown, <a href="https://github.com/lucasaugustus/oeis/blob/main/A193072.py">A193072.py</a>
%o A193072 (PARI) forstep(N=1, 1e7, 2, isprime(numerator(sigma(N^2)/N^2)) && !isprime(sigma(N^2)) && print1(N", "))
%Y A193072 Intersection of A193066 and A193071.
%K A193072 nonn,hard,more
%O A193072 1,1
%A A193072 _M. F. Hasler_, Jul 15 2011
%E A193072 a(8)-a(10) from _Donovan Johnson_, Sep 19 2011
%E A193072 a(11) from _Lucas A. Brown_, Apr 12 2021