%I #7 Sep 26 2021 23:21:15
%S 20,1,11,10,8,3,38,5,17,4,6,19,9,16,24,14,21,27,12,2,25,36,28,15,32,
%T 43,18,23,74,33,37,39,42,29,44,22,31,46,45,56,47,52,26,48,61,60,41,49,
%U 53,73,59,13,57,91,64,40,66,62,51,7,30,58,101,55,70,69,86,34,75,65,80,78,50
%N a(n) = index of n in A308387, or -1 if n does not appear in A308387.
%H N. J. A. Sloane, <a href="/A347691/b347691.txt">Table of n, a(n) for n = 1..6867</a>
%e A308387(20) = 1, so a(1) = 20.
%Y Cf. A308387.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Sep 26 2021