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 A191905 #23 Jul 14 2024 13:06:50
%S A191905 4,9,10,25,33,39,49,57,91,93,98,105,111,119,121,145,155,169,183,185,
%T A191905 187,189,201,205,209,215,225,235,237,242,245,265,289,291,299,305,327,
%U A191905 335,351,355,361,371,403,413,415,417,425,427,437,469,471,475,485,493,497,515,527,529,535,543,549,553
%N A191905 Composite deficient numbers k such that (product of proper divisors of k) mod (sum of proper divisors of k) is a prime number.
%H A191905 Harvey P. Dale, <a href="/A191905/b191905.txt">Table of n, a(n) for n = 1..1000</a>
%p A191905 isA191905 := proc(n) if not isA125493(n) then false; else isprime( A191906(n)) ; end if; end proc:
%p A191905 for n from 3 to 710 do if isA191905(n) then printf("%d,",n) ; end if; end do: # _R. J. Mathar_, Jun 27 2011
%t A191905 fQ[n_]:=Module[{pd=Most[Divisors[n]]},!PerfectNumberQ[n]&&CompositeQ[n] && DivisorSigma[ 1,n]<2n&& PrimeQ[Mod[Times@@pd,Total[pd]]]] Select[Range[2,600],fQ] (* _Harvey P. Dale_, Jul 14 2024 *)
%Y A191905 Cf. A001065, A005100, A007956, A125493, A191906.
%K A191905 nonn,less
%O A191905 1,1
%A A191905 _Juri-Stepan Gerasimov_, Jun 19 2011
%E A191905 Corrected by _R. J. Mathar_, Jun 27 2011