[seqfan] Re: Are these interesting?

zak seidov zakseidov at yahoo.com
Tue Jul 6 09:50:12 CEST 2010


1. earliest sequence such that xy | a(x+y)

- this may be all one's (A000012), right?

--- On Tue, 7/6/10, Andrew Weimholt <andrew.weimholt at gmail.com> wrote:

From: Andrew Weimholt <andrew.weimholt at gmail.com>
Subject: [seqfan]  Are these interesting?
To: "Sequence Fanatics Discussion list" <seqfan at list.seqfan.eu>
Date: Tuesday, July 6, 2010, 1:49 AM

1. earliest sequence such that xy | a(x+y)

1, 1, 2, 12, 12, 360, 60, 1680, 2520, 25200, 2520, 332640, 27720,
5045040, 5405400, 2882880,
720720, 220540320, 12252240, 4655851200, 4888643760, 5121436320,
232792560, 128501493120,
26771144400, 696049754400, 240940299600, 2248776129600, 80313433200,
69872686884000, 2329089562800, 1155228423148800,
4765317245488800, 4909720798382400, 5054124351276000,
5198527904169600, 144403552893600, 203031395368401600,

2. earliest sequence such that (x+y) | a(xy)

2, 3, 4, 20, 6, 35, 8, 18, 30, 77, 12, 728, 14, 45, 16, 680,
18, 1881, 20, 252, 110, 299, 24, 3850, 130, 135, 84, 5104, 30, 75361, 32, 396,
238, 665, 36, 28860, 38, 273, 80, 82082, 42, 218569, 44, 360, 2898,
1175, 48, 193648,
350, 2295, 260, 25228, 54, 33495, 112, 1710, 638, 1829, 60, 14501408,
62, 693, 192, 17680,
198, 199325, 68, 5796, 910, 848521, 72, 14005926, 74, 975, 2660,
70840, 234, 1784689, 80, 4536,

3. earliest sequence such that xy | a(x+y) and (x+y) | a(xy)

2, 3, 4, 60, 12, 2520, 120, 5040, 2520, 277200, 2520, 4324320, 27720,
5045040, 10810800, 49008960,
720720, 4190266080, 12252240, 4655851200, 4888643760, 117793035360,
232792560, 642507465600,
26771144400, 2088149263200, 240940299600, 65214507758400, 80313433200,
2166053293404000,
4658179125600, 1155228423148800, 4765317245488800, 4909720798382400,
5054124351276000,

Andrew


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