A079008 a(n) is smallest number k such that the n successive values of phi(k+j) (j=0,..,n-1) are all distinct.

1, 2, 5, 11, 11, 17, 17, 37, 46, 46, 112, 112, 123, 149, 149, 149, 257, 257, 257, 257, 257, 257, 257, 261, 658, 658, 685, 741, 741, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 1359, 4097, 4097, 4097, 4097, 4097

Offset

1,2

Links

Table of n, a(n) for n=1..50.

Example

a(8)=37, values of phi(k) for k=37,..,44 are {36, 18, 24, 16, 40, 12, 42, 20}.

Mathematica

kul[x_] := Length[x]-Length[Union[x]]; frt[x_] := Table[EulerPhi[x+j], {j, 0, h-1}]; Table[fa=1; k=0; Do[s=frt[n]; s1=kul[s]; If[Equal[s1, 0]&&Equal[fa, 1], k=k+1; Print[{h, n, s}]; fa=0], {n, 1, 10000}], {h, 1, 50}]

Prog

(PARI) a(n) = if(n==1, 1, my(v=vector(n, i, eulerphi(i))); for(k=n, oo, if(#Set(v)==n, return(k-n)); v[k%n+1]=eulerphi(k))); \\ Jinyuan Wang, Feb 10 2021

Crossrefs

Cf. A048892, A079007, A079009.

Sequence in context: A276736 A069162 A300677 * A144573 A062251 A091114

Adjacent sequences: A079005 A079006 A079007 * A079009 A079010 A079011

Keyword

nonn

Author

Labos Elemer, Jan 08 2003

Status

approved