cp's OEIS Frontend

A367614 a(n) is the unique k such that n is the comma-successor of k, or -1 if k does not exist.

%I A367614 #18 Dec 18 2023 14:50:35
%S A367614 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,10,1,-1,-1,-1,-1,-1,-1,-1,-1,-1,20,11,
%T A367614 2,-1,-1,-1,-1,-1,-1,-1,-1,30,21,12,3,-1,-1,-1,-1,-1,-1,-1,40,31,22,
%U A367614 13,4,-1,-1,-1,-1,-1,-1,50,41,32,23,14,-1,5,-1,-1,-1,-1,60,51,42,33,-1,24,15,6,-1,-1,-1,70,61,52,-1,43,34,25,16,7
%N A367614 a(n) is the unique k such that n is the comma-successor of k, or -1 if k does not exist.
%C A367614 If k exists, it could be called the comma-predecessor of n.
%C A367614 a(n) is the unique k such that A367338(k) = n, or -1.
%C A367614 a(n) = -1 iff n is in A367600.
%H A367614 Michael S. Branicky, <a href="/A367614/b367614.txt">Table of n, a(n) for n = 1..10000</a>
%o A367614 (Python)
%o A367614 def a(n):
%o A367614     y = int(str(n)[0])
%o A367614     x = (n-y)%10
%o A367614     k = n - y - 10*x
%o A367614     kk = k + 10*x + y-1
%o A367614     return k if k > 0 and int(str(kk)[0]) != y-1 else -1
%o A367614 print([a(n) for n in range(1, 86)]) # _Michael S. Branicky_, Dec 16 2023
%Y A367614 Cf. A121805, A367600, A367338.
%K A367614 sign,base
%O A367614 1,11
%A A367614 _N. J. A. Sloane_, Dec 16 2023