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.
%I A079449 #14 Apr 19 2025 03:51:07
%S A079449 2,5,7,11,13,23,41,47,59,61,73,83,89,107,109,137,157,167,179,193,227,
%T A079449 229,233,241,263,271,277,313,337,347,349,359,373,379,383,409,433,449,
%U A079449 457,461,467,479,503,563,569,587,709,719,733,809,821,839,853,857,863
%N A079449 Primes p such that there is at least one integer x satisfying p = x*tau(x)+1 where tau(x) = A000005(x), the number of divisors of x.
%H A079449 Amiram Eldar, <a href="/A079449/b079449.txt">Table of n, a(n) for n = 1..10000</a>
%e A079449 12*tau(12) = 72 hence 73 is in the sequence.
%t A079449 seq[lim_] := Union[Select[Table[k * DivisorSigma[0, k] + 1, {k, 1, Floor[lim/2]}], # <= lim && PrimeQ[#] &]]; seq[1000] (* _Amiram Eldar_, Apr 19 2025 *)
%o A079449 (PARI) lista(nn) = {forprime(p=2, nn, for (n=1, p, if (n*numdiv(n)+1 == p, print1(p, ", "); break;);););} \\ _Michel Marcus_, Dec 01 2013
%Y A079449 Cf. A000005, A079448, A083271.
%K A079449 nonn
%O A079449 1,1
%A A079449 _Benoit Cloitre_, Jan 13 2003