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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). 1

%I

%S 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 18,11,19,12,9,13,20,21,14,22,23,24,15,11,9,16,12,17,25,18,26,27,19,

%U 14,9,11,28,20,15,21,29,30,22,31,23,17,24,11,18,32,33

%N 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 a(n) = A094173(n) for n<16.

%e 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 (Python)

%o SIZE = 300

%o a = [-8]*SIZE

%o top=0

%o for n in range(SIZE):

%o if a[n]==-8: # if a[n] is undefined yet

%o top+=1

%o a[n]=top

%o if n+1+a[n]<SIZE and a[n+1+a[n]]==-8: # if a[n+1+a[n]] is undefined yet

%o a[n+1+a[n]]=a[n]

%o print(a[n], end=',')

%Y Cf. A094173.

%Y Cf. A214371.

%K nonn,easy

%O 1,2

%A _Alex Ratushnyak_, Jul 14 2012

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Last modified October 20 22:22 EDT 2021. Contains 348119 sequences. (Running on oeis4.)