cp's OEIS Frontend

A225714 Composite squarefree numbers n such that p(i)+4 divides n-4, where p(i) are the prime factors of n.

%I A225714 #11 Nov 15 2013 05:27:03
%S A225714 1054,9541,91039,371074,985054,1043959,1063003,1107754,1162498,
%T A225714 1357339,1786054,4018018,5368549,5820154,8725747,9994954,12402709,
%U A225714 17138503,17914054,20855839,23116009,25077199,26545054,29247229,30308359,31424419,33892759,44141629
%N A225714 Composite squarefree numbers n such that p(i)+4 divides n-4, where p(i) are the prime factors of n.
%e A225714 Prime factors of 1043959 are 7, 293 and 509. We have that (1043959-4)/(7+4) = 94905, (1043959-4)/(293+4) = 3515 and (1043959-4)/(509+4) = 2035.
%p A225714 with(numtheory); A225714:=proc(i,j) local c, d, n, ok, p, t;
%p A225714 for n from 2 to i do if not isprime(n) then p:=ifactors(n)[2]; ok:=1;
%p A225714 for d from 1 to nops(p) do if p[d][2]>1 or p[d][1]=j then ok:=0; break; fi;
%p A225714 if  not type((n+j)/(p[d][1]-j),integer) then ok:=0; break; fi; od;
%p A225714 if ok=1 then print(n); fi; fi; od; end: A225714(10^9,-4);
%Y A225714 Cf. A208728, A225702-A225713, A225715-A225720.
%K A225714 nonn
%O A225714 1,1
%A A225714 _Paolo P. Lava_, May 13 2013
%E A225714 a(20)-a(28) from _Donovan Johnson_, Nov 15 2013