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 A192420 Smallest k such that 1^4, 2^4, 3^4,... ,n^4 are distinct modulo k. 4
 1, 2, 6, 9, 11, 14, 14, 18, 19, 22, 22, 31, 31, 31, 31, 38, 38, 38, 38, 43, 43, 46, 46, 59, 59, 59, 59, 59, 59, 62, 62, 67, 67, 71, 71, 79, 79, 79, 79, 83, 83, 86, 86, 94, 94, 94, 94, 103, 103, 103, 103, 107, 107, 118, 118, 118, 118, 118, 118, 127, 127, 127, 127, 131, 131, 134, 134, 139, 139 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS The discriminator D(4,n). LINKS Alois P. Heinz, Table of n, a(n) for n = 1..1000 P. Moree, H. Roskam, On an arithmetical function related to Euler's totient and the discriminator, Fib. Quart. 33 (4) (1995), 332-340 MAPLE dis := proc(j, n) local k, s, i; for k from 1 do s := {} ; for i from 1 to n do s := s union { (i^j) mod k} ; end do: if nops(s) = n then return k; end if; end do: end proc: A192420 := proc(n) dis(4, n) ; end proc: MATHEMATICA a[n_] := For[k = 1, True, k++, If[Unequal @@ PowerMod[Range[n], 4, k], Return[k]]]; Array[a, 100] (* Jean-François Alcover, May 18 2018 *) PROG (PARI) A192420(nMax, f=n->n^4)={my(S=[], a=1); vector(nMax, n, S=concat(S, f(n)); while(#Set(S%a)

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Last modified September 21 08:38 EDT 2020. Contains 337268 sequences. (Running on oeis4.)