A255833 - OEIS

%I #26 May 18 2019 14:05:03

%S 1,2,4,3,8,7,6,5,12,11,10,9,16,15,14,13,21,20,19,18,17,24,23,22,29,28,

%T 27,26,40,39,38,37,36,35,34,33,32,31,30,41,42,43,44,45,46,47,48,49,50,

%U 51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66,67,68,69,25

%N Index i such that A166133(i)=n, or 0 if no such i exists.

%C If A166133 is a permutation, as conjectured, then this is the inverse permutation.

%H M. F. Hasler, <a href="/A255833/b255833.txt">Table of n, a(n) for n = 1..10000</a>

%H Ray Chandler, <a href="/A255833/a255833.txt">Table of n, a(n) for n=1..3743853</a> (55 MB)

%o (PARI) a(n)=for(i=1,#a166133,a166133[i]==n&&return(i)) \\ assumes a166133 defined as a vector, e.g., via {c=0; a166133=apply(t->eval(concat(Vec(t)[1+#Str(c++) .. -1])), readstr("/tmp/b166133.txt"))}

%o (Haskell)

%o import Data.List (elemIndex); import Data.Maybe (fromJust)

%o a255833 = (+ 1) . fromJust . (`elemIndex` a166133_list)

%o -- _Reinhard Zumkeller_, Apr 02 2015

%Y Cf. A166133, A256561, A256563.

%K nonn

%O 1,2

%A _M. F. Hasler_, Apr 01 2015

%E Definition simplified by _Franklin T. Adams-Watters_, Apr 01 2015