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 A302127 Primitive terms of A067808. 1
 720, 1080, 1680, 1800, 2016, 2520, 3024, 3780, 3960, 4200, 4680, 5280, 5544, 6120, 6300, 6840, 7056, 9240, 9504, 9600, 10584, 10920, 11232, 12480, 12672, 13104, 13200, 13860, 14256, 14280, 15600, 16380, 17136, 19152, 19656, 20400, 20592, 21420, 23184, 23940, 24000, 25704, 26928, 28728, 29232 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Terms of A067808 that are not divisible by any smaller term of A067808. For any set S of primes whose sum of reciprocals is infinite, there are members whose prime factors are all in S. For example, by the strong form of Dirichlet's theorem this is the case for an arithmetic progression {x: x == c (mod d)} if c and d are coprime. LINKS Robert Israel, Table of n, a(n) for n = 1..10000 MAPLE count:= 0: Res:= NULL: for n from 1 while count < 100 do F:= ifactors(n)[2]; if mul((t[1]^(t[2]+1)-1)^2/(t[1]^(2*t[2]+1)-1)/(t[1]-1), t = F) > 3 and andmap(s -> not(type(n/s, integer)), [Res]) then count:= count+1; Res:= Res, n; fi od: Res; MATHEMATICA count = 0; Res = {}; For[n = 2, count < 100, n++, F = FactorInteger[n]; If[Product[{p, e} = pe; (p^(e+1)-1)^2/((p^(2e+1)-1)(p-1)), {pe, F}] > 3 && AllTrue[Res, !IntegerQ[n/#]&], count++; AppendTo[Res, n]] ]; Res (* Jean-François Alcover, Apr 29 2019, after Robert Israel *) CROSSREFS Cf. A067808. Sequence in context: A137493 A179669 A067808 * A291804 A131663 A090392 Adjacent sequences: A302124 A302125 A302126 * A302128 A302129 A302130 KEYWORD nonn AUTHOR Robert Israel, Jun 20 2018 STATUS approved

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Last modified July 13 02:50 EDT 2024. Contains 374265 sequences. (Running on oeis4.)