%I #17 Feb 01 2019 03:03:25

%S 1,2,3,4,5,3,3,5,5,4,5,5,3,4,3,4,4,6,6,6,6,6,5,4,7,6,5,6,5,6,5,5,5,4,

%T 5,5,6,5,6,6,5,5,5,7,7,7,5,5,6,6,7,7,6,7,6,6,7,6,7,6,6,7,8,7,7,8,8,8,

%U 9,4,5,5,6,4,5,6,5,6,6,4,5,4,6,5,5,4,5,4,7,5,5,4,7,6,7,8,5,8,6,6,6,6,6,7,7

%N a(0)=1. a(n) = a(prime(n)(mod n)) + 1, where prime(n) is the n-th prime.

%e The 7th prime, 17, is congruent to 3 (mod 7). So a(7) = a(3) + 1 = 4 + 1 = 5.

%p a[0]:=1: for n from 1 to 125 do a[n]:=1+a[ithprime(n) mod n] od: seq(a[n],n=0..125); # _Emeric Deutsch_, Mar 25 2007

%t f[l_List] := Block[{n = Length[l]},Append[l, l[[Mod[Prime[n], n] + 1]] + 1]];Nest[f, {1}, 105] (* _Ray Chandler_, Mar 25 2007 *)

%o (PARI) a(n)={k=1;if(n>0,k=a(prime(n)%n)+1);k;} \\ _Jinyuan Wang_, Feb 01 2019

%Y Cf. A004648, A127066.

%K nonn

%O 0,2

%A _Leroy Quet_, Mar 21 2007

%E Extended by _Ray Chandler_ and _Emeric Deutsch_, Mar 25 2007