A175076 Composites c which end at 2 under iterations of {r mod (max prime p < r)} starting at r = c.
9, 15, 21, 25, 28, 33, 36, 39, 45, 49, 52, 55, 58, 63, 66, 69, 75, 78, 81, 85, 88, 91, 94, 96, 99, 105, 111, 115, 118, 120, 122, 126, 129, 133, 136, 141, 144, 146, 148, 153, 156, 159, 162, 165, 169, 172, 175, 178, 183, 186, 188, 190, 195, 201, 204, 206, 208, 213, 216
Offset: 1
Keywords
Examples
Iteration procedure for a(2) = 15: 15 mod 13 = 2. Iteration procedure for a(5) = 28: 28 mod 23 = 5, 5 mod 3 = 2.
Programs
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Mathematica
ce2Q[n_]:=NestWhileList[Mod[#,NextPrime[#,-1]]&,n,#>0&][[-2]]==2; Select[ Range[ 300],CompositeQ[#]&&ce2Q[#]&] (* Harvey P. Dale, Feb 09 2015 *)
Extensions
More terms from R. J. Mathar, Sep 25 2010
Comments