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 A216918 Odd numbers with at least 3 distinct prime factors. 2
 105, 165, 195, 231, 255, 273, 285, 315, 345, 357, 385, 399, 429, 435, 455, 465, 483, 495, 525, 555, 561, 585, 595, 609, 615, 627, 645, 651, 663, 665, 693, 705, 715, 735, 741, 759, 765, 777, 795, 805, 819, 825, 855, 861, 885, 897, 903, 915, 935, 945, 957, 969 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS If "at least" is changed to "exactly" we get A278569. - N. J. A. Sloane, Nov 27 2016 LINKS Alois P. Heinz, Table of n, a(n) for n = 1..10000 J. B. Cosgrave, K. Dilcher, Extensions of the Gauss-Wilson Theorem, Integers: Electronic Journal of Combinatorial Number Theory, 8 (2008), p.11. FORMULA Gauss_factorial(floor(a(n)/2), a(n)) == 1 (mod a(n)). (Cf. A216919) MAPLE a:= proc(n) option remember; local k;       for k from 2+ `if`(n=1, 103, a(n-1)) by 2         while nops(numtheory[factorset](k))<=2 do od; k     end: seq (a(n), n=1..100);  # Alois P. Heinz, Oct 03 2012 MATHEMATICA Select[Range[1, 999, 2], (PrimeNu[#] >= 3)&] (* Jean-François Alcover, Feb 27 2014 *) PROG (Sage) def is_A216918(n):     if n % 2 == 0: return False     return len(n.prime_divisors()) >= 3 def A216918_list(n): return [k for k in srange(1, n + 1, 2) if is_A216918(k)] A216918_list(969) CROSSREFS A278569 is a subsequence. Sequence in context: A252069 A133509 A013590 * A278569 A046389 A154430 Adjacent sequences:  A216915 A216916 A216917 * A216919 A216920 A216921 KEYWORD nonn AUTHOR Peter Luschny, Oct 02 2012 STATUS approved

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Last modified August 11 06:25 EDT 2020. Contains 336422 sequences. (Running on oeis4.)