cp's OEIS Frontend

A228300 Composite squarefree numbers n such that p-d(n) divides n-d(n), where p are the prime factors of n and d(n) the number of divisors of n.

%I A228300 #14 Sep 23 2013 06:08:37
%S A228300 6,10,15,110,170,273,638,935,1394,2093,2438,2465,4823,5453,7973,11978,
%T A228300 16354,17963,34918,43337,46943,62491,64583,68266,71603,72046,74347,
%U A228300 75361,85877,134458,148291,155933,186235,188071,201994,209933,280891,307021,367081
%N A228300 Composite squarefree numbers n such that p-d(n) divides n-d(n), where p are the prime factors of n and d(n) the number of divisors of n.
%C A228300 Subsequence of A120944.
%H A228300 Donovan Johnson, <a href="/A228300/b228300.txt">Table of n, a(n) for n = 1..500</a>
%e A228300 Prime factors of 17963 are 11, 23 and 71 while d(17963) = 8. We have that 17963 - 8 = 17955 and 17955 / (11 - 8) =  5985, 17955 / (23 - 8) = 1197 and 17955 / (71 - 8) = 285.
%p A228300 with (numtheory); P:=proc(q) local a,b,c,i,ok,p,n;
%p A228300 for n from 2 to q do  if not isprime(n) then a:=ifactors(n)[2]; ok:=1;
%p A228300 for i from 1 to nops(a) do if a[i][2]>1 or a[i][1]=tau(n) then ok:=0; break;
%p A228300 else if not type((n-tau(n))/(a[i][1]-tau(n)),integer) then ok:=0; break; fi; fi; od; if ok=1 then print(n); fi; fi; od; end: P(10^6);
%Y A228300 Cf. A000005, A228299, A228301, A228302.
%K A228300 nonn
%O A228300 1,1
%A A228300 _Paolo P. Lava_, Aug 20 2013
%E A228300 First term deleted by _Paolo P. Lava_, Sep 23 2013