A192420 Smallest k such that 1^4, 2^4, 3^4,... ,n^4 are distinct modulo k.

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

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)<n, a++); a)} \\ M. F. Hasler, May 04 2016

Crossrefs

Cf. A016726, A192419.

Sequence in context: A146974 A133160 A128906 * A139639 A187690 A045038

Adjacent sequences: A192417 A192418 A192419 * A192421 A192422 A192423

Keyword

nonn

Author

R. J. Mathar, Jun 30 2011

Status

approved