cp's OEIS Frontend

A383186 Inverse permutation to A383185 (square spiral numbers of king filling the two-dimensional grid always crossing the spiral's wall).

%I A383186 #11 May 21 2025 23:24:00
%S A383186 0,5,3,1,10,25,8,6,19,17,4,15,13,2,11,30,28,26,9,24,22,7,20,18,43,41,
%T A383186 74,16,14,37,35,33,12,31,29,60,58,27,56,54,23,52,50,48,21,46,44,42,79,
%U A383186 77,75,40,73,38,36,69,67,34,65,32,63,61,59,100,98,147,57,55,94,53,51,90,88,49,86
%N A383186 Inverse permutation to A383185 (square spiral numbers of king filling the two-dimensional grid always crossing the spiral's wall).
%H A383186 <a href="/index/Per#IntegerPermutation">OEIS index to sequences related to permutations of the integers</a>.
%o A383186 (Python)
%o A383186 def A383186(n):
%o A383186     if not hasattr(A:=A383186, 'terms'): A.terms=[0]; A.N=1
%o A383186     while len(t := A.terms) <= n:
%o A383186        try: any(t.append(A383185.terms.index(k))for k in range(len(t), n+1))
%o A383186        except: A.N = A.N*5//4+99; A383185(A.N)
%o A383186     return A.terms[n]
%Y A383186 Cf. A383185.
%K A383186 nonn
%O A383186 0,2
%A A383186 _M. F. Hasler_, May 12 2025