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 A242871 Numbers n such that (n^n-3^3)/(n-3) is an integer. 3
 1, 2, 4, 5, 6, 7, 9, 11, 12, 15, 19, 21, 23, 27, 30, 35, 39, 42, 43, 45, 51, 57, 63, 67, 75, 81, 83, 87, 99, 103, 111, 120, 123, 129, 131, 147, 159, 163, 171, 183, 195, 203, 219, 223, 237, 243, 255, 259, 275, 291, 297, 303, 315, 323, 331, 339, 345, 354, 363, 381, 387 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS These are also numbers n such that (n^3-3^n)/(n-3) is an integer. LINKS Robert Israel, Table of n, a(n) for n = 1..1149 EXAMPLE (5^5-3^3)/(5-3) = 3098/2 = 1549 is an integer. Thus 5 is a member of this sequence. MAPLE filter:= proc(n) (n^n - 27) mod (n-3) = 0 end proc: select(filter, [1, 2, \$4..1000]); # Robert Israel, May 25 2014 MATHEMATICA Join[{1, 2}, Select[Range[4, 400], IntegerQ[(#^#-27)/(#-3)]&]] (* Harvey P. Dale, Dec 17 2014 *) PROG (PARI) for(n=1, 1000, if(n!=3, s=(n^n-3^3)/(n-3); if(floor(s)==s, print(n)))) CROSSREFS Cf. A242870. Sequence in context: A099593 A184867 A029903 * A026420 A026479 A242788 Adjacent sequences:  A242868 A242869 A242870 * A242872 A242873 A242874 KEYWORD nonn AUTHOR Derek Orr, May 24 2014 STATUS approved

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Last modified September 23 02:41 EDT 2021. Contains 347609 sequences. (Running on oeis4.)