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 A054396 Numbers n such that there are precisely 4 groups of order n. 22
 28, 30, 44, 63, 66, 70, 76, 92, 102, 117, 124, 130, 138, 154, 170, 172, 174, 182, 188, 190, 230, 236, 238, 246, 266, 268, 275, 279, 282, 284, 286, 290, 315, 316, 318, 322, 332, 354, 370, 374, 387, 412, 418, 426, 428, 430, 434, 442, 465, 470, 494, 495, 498 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Muniru A Asiru, Table of n, a(n) for n = 1..369 H. U. Besche, B. Eick and E. A. O'Brien, The Small Groups Library Gordon Royle, Numbers of Small Groups FORMULA Sequence is { k | A000001(k) = 4 }. - Muniru A Asiru, Nov 04 2017 EXAMPLE For n = 28, the 4 groups of order 8 are C7 : C4, C28, D28, C14 x C2 and for n = 30 the 4 groups of order 30 are C5 x S3, C3 x D10, D30, C30 where C, D mean Cyclic, Dihedral groups of the stated order and S is the Symmetric group of the stated degree. The symbols x and : mean direct and semidirect products respectively. - Muniru A Asiru, Nov 04 2017 MATHEMATICA Select[Range[500], FiniteGroupCount[#] == 4 &] (* Jean-François Alcover, Dec 08 2017 *) PROG (GAP) A054396 := Filtered([1..2015], n -> NumberSmallGroups(n) = 4); # Muniru A Asiru, Nov 04 2017 CROSSREFS Cf. A000001, A003277, A054395, A054397, A055561, A054396, A135850. Sequence in context: A042622 A044977 A046466 * A083274 A067913 A116566 Adjacent sequences:  A054393 A054394 A054395 * A054397 A054398 A054399 KEYWORD nonn AUTHOR N. J. A. Sloane, May 21 2000 EXTENSIONS More terms from Christian G. Bower, May 25 2000 STATUS approved

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Last modified August 6 17:06 EDT 2020. Contains 336255 sequences. (Running on oeis4.)