cp's OEIS Frontend

A214370 If a(n) has not yet been defined then set a(n) = least positive integer that has not yet occurred; also if a(n+1+a(n)) has not yet been defined then set a(n+1+a(n)) = a(n).

%I A214370 #23 May 22 2021 14:34:34
%S A214370 1,2,1,3,2,4,5,3,6,7,4,3,5,8,9,6,10,7,5,11,12,13,8,14,9,7,15,10,16,17,
%T A214370 18,11,19,12,9,13,20,21,14,22,23,24,15,11,9,16,12,17,25,18,26,27,19,
%U A214370 14,9,11,28,20,15,21,29,30,22,31,23,17,24,11,18,32,33
%N A214370 If a(n) has not yet been defined then set a(n) = least positive integer that has not yet occurred; also if a(n+1+a(n)) has not yet been defined then set a(n+1+a(n)) = a(n).
%C A214370 a(n) = A094173(n) for n<16.
%e A214370 a(1) = 1 because this is the first undefined place and unused number. This "throws" a copy of the 1 forward to a(1+1+1)=a(3)=1. a(2)=2 uses the next new integer, and this copies the 2 forward to a(2+1+2)=a(5)=2. a(3) is already defined then, and a(4) receives the hitherto unused 3.
%o A214370 (Python)
%o A214370 SIZE = 300
%o A214370 a = [-8]*SIZE
%o A214370 top=0
%o A214370 for n in range(SIZE):
%o A214370     if a[n]==-8:       # if a[n] is undefined yet
%o A214370         top+=1
%o A214370         a[n]=top
%o A214370     if n+1+a[n]<SIZE and a[n+1+a[n]]==-8:   # if a[n+1+a[n]] is undefined yet
%o A214370         a[n+1+a[n]]=a[n]
%o A214370     print(a[n], end=',')
%Y A214370 Cf. A094173.
%Y A214370 Cf. A214371.
%K A214370 nonn,easy
%O A214370 1,2
%A A214370 _Alex Ratushnyak_, Jul 14 2012