cp's OEIS Frontend

A229274 Composite squarefree numbers n such that p+tau(n) divides n-sigma(n), where p are the prime factors of n, tau(n) = A000005(n) and sigma(n) = A000203(n).

%I A229274 #19 Feb 22 2018 14:52:16
%S A229274 51,93,177,219,303,471,597,681,723,807,849,933,1059,1101,1227,1437,
%T A229274 1563,1689,1731,1857,1941,1983,2319,2361,2487,2571,2823,2949,2991,
%U A229274 3117,3327,3369,3453,3579,3747,3831,3873,3957,4083,4377,4461,4629,4713,4839,4881
%N A229274 Composite squarefree numbers n such that p+tau(n) divides n-sigma(n), where p are the prime factors of n, tau(n) = A000005(n) and sigma(n) = A000203(n).
%C A229274 Subsequence of A120944.
%H A229274 Paolo P. Lava, <a href="/A229274/b229274.txt">Table of n, a(n) for n = 1..999</a>
%e A229274 Prime factors of 177 are 3, 59 and sigma(177) = 240 , tau(177) = 4.
%e A229274 177 - 240 = -63 and (-63) / (3 + 4) = -9, (-63) / (59 + 4) = -1.
%p A229274 with (numtheory); P:=proc(q) local a, b, c, i, ok, p, n;
%p A229274 for n from 2 to q do  if not isprime(n) then a:=ifactors(n)[2]; ok:=1;
%p A229274 for i from 1 to nops(a) do if a[i][2]>1 then ok:=0; break;
%p A229274 else if not type((n-sigma(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 A229274 Cf. A000005, A000203.
%Y A229274 Cf. A228299, A228300, A228301, A228302, A229273, A229275, A229276.
%K A229274 nonn
%O A229274 1,1
%A A229274 _Paolo P. Lava_, Sep 19 2013
%E A229274 First term deleted by _Paolo P. Lava_, Sep 23 2013