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 A219960 Numbers which do not reach zero under the repeated iteration x -> ceiling(sqrt(x)) * (ceiling(sqrt(x))^2 - x). 4
 366, 680, 691, 1026, 1136, 1298, 1323, 1417, 1464, 1583, 1604, 1702, 2079, 2125, 2222, 2223, 2374, 2507, 2604, 2627, 2821, 2844, 2897, 3152, 3157, 3159, 3183, 3210, 3231, 3459, 3697, 3715, 3762, 3802, 3866, 3888, 3936, 3948, 4004, 4111, 4133, 4145, 4231, 4299 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Ceiling equivalent of A219303, with somewhat different behavior despite a near-identical iterative process. Conjecture #1: All numbers under the iteration reach 0 or, like the elements of this sequence, reach a finite loop, and none expand indefinitely to infinity. Conjecture #2: There are an infinite number of such finite loops, though there is often significant distance between them. Conjecture #3: There are an infinite number of pairs of consecutive integers in this sequence despite being less abundant than in A219303. LINKS Carl R. White, Table of n, a(n) for n = 1..10000 EXAMPLE 1702 is in this list as 38 iterations return to 1702. Many other numbers reach this loop. 5832 is also in this list and is the smallest member of a different loop. 1703 is _not_ in this list because the iteration runs: 1703 -> 2562 -> 1989 -> 1620 -> 2501 -> 5100 -> 6048 -> 2808 -> 53 -> 88 -> 120 -> 11 -> 20 -> 25 -> 0. MATHEMATICA f[n_] := Ceiling[Sqrt[n]]*(Ceiling[Sqrt[n]]^2 - n); Select[Range[5000], NestWhileList[f, #, UnsameQ, All][[-1]] > 0 &] (* T. D. Noe, Dec 04 2012 *) CROSSREFS Cf. A219303, A219961, A219962, A219963 Sequence in context: A073305 A248552 A259077 * A033174 A249704 A260281 Adjacent sequences:  A219957 A219958 A219959 * A219961 A219962 A219963 KEYWORD nonn AUTHOR Carl R. White, Dec 02 2012 STATUS approved

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Last modified October 13 21:59 EDT 2019. Contains 327981 sequences. (Running on oeis4.)