cp's OEIS Frontend

A255423 The least number k > A255334(n) for which A000203(k) = A000203(A255334(n)) and A007947(k) = A007947(A255334(n)), where A000203 gives the sum of divisors, and A007947 gives the squarefree kernel of n.

%I A255423 #9 Jul 19 2016 12:29:59
%S A255423 2058,10290,22638,26754,34986,39102,47334,51450,59682,52728,63798,
%T A255423 76146,84378,88494,96726,109074,113190,121422,125538,133770,137886,
%U A255423 146118,150234,162582,170814,174930,183162,195510,199626,207858,211974,220206,224322,232554,236670,249018,257250,261366,269598,281946,286062,294294
%N A255423 The least number k > A255334(n) for which A000203(k) = A000203(A255334(n)) and A007947(k) = A007947(A255334(n)), where A000203 gives the sum of divisors, and A007947 gives the squarefree kernel of n.
%H A255423 Antti Karttunen, <a href="/A255423/b255423.txt">Table of n, a(n) for n = 1..6589</a>
%F A255423 a(n) = A255424(n) * A255426(n).
%o A255423 (PARI)
%o A255423 A007947(n) = factorback(factorint(n)[, 1]);
%o A255423 nextone(n) = { if(!n,return(0)); my(r=A007947(n), s=sigma(n), k=n+r); while(k<s, if((sigma(k) == s)&&(A007947(k) == r), return(k), k = k+r)); return(0); };
%o A255423 i=0; for(n=1, 2^25, k = nextone(n); if(k, i++; write("b255423.txt", i, " ", k))); \\ _Andrew Lelechenko_, May 09 2014
%Y A255423 Cf. A000203, A007947, A255334.
%Y A255423 Cf. also A255335 (same sequence sorted into ascending order), A255424 (squarefree kernel of a(n)), A255426 (same terms with but with their squarefree kernel divided out of them).
%K A255423 nonn
%O A255423 1,1
%A A255423 _Antti Karttunen_, Apr 06 2015