OFFSET
1,1
COMMENTS
None of the terms are squarefree, because if there were such x, then we would have rad(x) = x, and for any value k > x such that rad(k) = x we would have k = y*x, for some strictly positive integer y, and in that case sigma(k) > sigma(x). Thus all terms are members of sequence A013929.
None of the terms in range a(1) .. a(6589) occur in A255335. Are the sequences disjoint forever?
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..6589
PROG
(PARI)
A007947(n) = factorback(factorint(n)[, 1]); \\ Andrew Lelechenko, May 09 2014
isA255334(n) = { my(r=A007947(n), s=sigma(n), k=n+r); while(k<s, if((sigma(k) == s)&&(A007947(k) == r), return(1), k = k+r)); return(0); };
i=0; for(n=1, 2^25, if(isA255334(n), i++; write("b255334.txt", i, " ", n)))
(Scheme, with Antti Karttunen's IntSeq-library. Quite naive and slow implementation.)
(define A255334 (MATCHING-POS 1 1 isA255334?))
CROSSREFS
KEYWORD
nonn
AUTHOR
Antti Karttunen, Mar 23 2015
STATUS
approved