%I #13 Jul 23 2020 19:27:02
%S 1,1,2,2,3,3,4,3,5,5,4,4,7,3,6,8,5,5,6,5,8,8,5,6,10,5,8,8,9,7,7,8,9,9,
%T 8,9,12,5,8,12,8,9,10,7,13,9,13,11,10,7,9,12,11,9,11,10,18,8,8,10,16,
%U 10,9,12,11,11,14,13,13,12,10,15,12,10,15,11,15,12,11,13,14,12,12,13,18,9,14
%N a(1)=1. a(n) = number of earlier terms a(k), 1<=k<=n1, such that (k+n) is divisible by a(k).
%H Rémy Sigrist, <a href="/A127431/b127431.txt">Table of n, a(n) for n = 1..10000</a>
%H Rémy Sigrist, <a href="/A127431/a127431.txt">C program for A127431</a>
%e (1+11) is a multiple of a(1)=1; (2+11) is a multiple of a(2)=1; (3+11) is a multiple of a(3)=2; and (9+11) is a multiple of a(9)=5. These four cases are the only cases where (k+n) is divisible by a(k), for 1<=k<=10. So a(11) = 4.
%t f[l_List] := Block[{n = Length[l] + 1},Append[l, Count[Table[Mod[k + n, l[[k]]], {k, n  1}], 0]]];Nest[f, {1}, 86] (* _Ray Chandler_, Jan 22 2007 *)
%o (C) See Links section.
%Y Cf. A127432, A127433.
%K nonn,look
%O 1,3
%A _Leroy Quet_, Jan 14 2007
%E Extended by _Ray Chandler_, Jan 22 2007
