A265261 Smallest n-Knödel number, i.e., smallest composite c > n such that each b < c coprime to c satisfies b^(c-n) == 1 (mod c).

561, 4, 9, 6, 25, 8, 15, 12, 21, 12, 15, 16, 33, 24, 21, 20, 65, 24, 51, 24, 45, 24, 33, 32, 69, 30, 39, 40, 65, 36, 87, 40, 45, 44, 51, 40, 85, 56, 57, 48, 65, 72, 91, 48, 63, 66, 69, 60, 141, 56, 63, 60, 65, 72, 75, 60, 63, 70, 87, 72, 133, 122, 93, 80, 165

Offset

1,1

Links

Felix Fröhlich, Table of n, a(n) for n = 1..4000

Wikipedia, Knödel number.

Mathematica

Table[SelectFirst[Range[n + 1, 10^3], Function[c, CompositeQ@ c && AllTrue[Range[1, c - 1] /. x_ /; ! CoprimeQ[x, c] -> Nothing, Mod[#^(c - n), c] == 1 &]]], {n, 65}] (* Michael De Vlieger, Apr 06 2016, Version 10 *)

Prog

(PARI) a(n) = forcomposite(c=n+1, , my(i=0, j=0); for(b=1, c-1, if(gcd(b, c)==1, i++; if(Mod(b, c)^(c-n)==1, j++))); if(i==j, return(c)))

Crossrefs

Cf. A050990, A033553, A050992, A050993, A208154, A208155, A208156, A208157, A208158.

Sequence in context: A167822 A104590 A259211 * A234936 A274443 A247906

Adjacent sequences: A265258 A265259 A265260 * A265262 A265263 A265264

Keyword

nonn

Author

Felix Fröhlich, Apr 06 2016

Status

approved