cp's OEIS Frontend

A225719 Composite squarefree numbers n such that p(i)+9 divides n-9, where p(i) are the prime factors of n.

%I A225719 #8 May 17 2013 11:39:07
%S A225719 2193,3705,9889,12749,23529,116265,283929,514569,641769,661789,772809,
%T A225719 950609,1144313,1241561,1452009,1708233,1797609,1878569,2244901,
%U A225719 2255689,2675409,2792937,3426089,4021369,4187465,5242569,7327329,7942209,8601329,8668921,9608729
%N A225719 Composite squarefree numbers n such that p(i)+9 divides n-9, where p(i) are the prime factors of n.
%e A225719 Prime factors of 116265 are 3, 5, 23 and 337. We have that (116265-9)/(3+9) = 9688, (116265-9)/(5+9) = 8304, (116265-9)/(23+9) = 3633 and (116265-9)/(337+9) = 336.
%p A225719 with(numtheory); A225719:=proc(i,j) local c, d, n, ok, p, t;
%p A225719 for n from 2 to i do if not isprime(n) then p:=ifactors(n)[2]; ok:=1;
%p A225719 for d from 1 to nops(p) do if p[d][2]>1 or p[d][1]=j then ok:=0; break; fi;
%p A225719 if  not type((n+j)/(p[d][1]-j),integer) then ok:=0; break; fi; od;
%p A225719 if ok=1 then print(n); fi; fi; od; end: A225719(10^9,-9);
%Y A225719 Cf. A208728, A225702-A225718, A225720.
%K A225719 nonn
%O A225719 1,1
%A A225719 _Paolo P. Lava_, May 13 2013