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 A255334 Numbers n for which there exists k > n such that A000203(k) = A000203(n) and A007947(k) = A007947(n), where A000203 gives the sum of divisors, and A007947 gives the squarefree kernel of n. 8
 1512, 7560, 16632, 19656, 25704, 28728, 34776, 37800, 43848, 44928, 46872, 55944, 61992, 65016, 71064, 80136, 83160, 89208, 92232, 98280, 101304, 107352, 110376, 119448, 125496, 128520, 134568, 143640, 146664, 152712, 155736, 161784, 164808, 170856, 173880, 182952, 189000, 192024, 198072, 207144, 210168, 216216 (list; graph; refs; listen; history; text; internal format)
 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 FORMULA a(n) = A255424(n) * A255425(n). 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= try sig_n) #f) ((and (= sig_n (A000203 try)) (= rad_n (A007947 try))) #t) (else (loop (+ try rad_n))))))) CROSSREFS Subsequence of A013929. Cf. A000203, A007947. Cf. also A255423 (gives the corresponding k), A255335 (same sequence sorted into ascending order, with duplicates removed), A255412 [gives sigma(a(n))], A255424 [gives rad(a(n))], A255425, A254035, A254791. Sequence in context: A060676 A230402 A248718 * A255778 A236091 A239175 Adjacent sequences:  A255331 A255332 A255333 * A255335 A255336 A255337 KEYWORD nonn AUTHOR Antti Karttunen, Mar 23 2015 STATUS approved

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Last modified August 20 10:41 EDT 2019. Contains 326150 sequences. (Running on oeis4.)