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A214371 If a(n) has not yet been defined then set a(n) = least positive integer that has not yet occurred; also if n>1 and a(n+a(n)) has not yet been defined then set a(n+a(n)) = a(n). 1

%I

%S 1,2,3,2,4,3,5,6,4,7,8,5,4,6,9,10,7,11,8,6,12,13,14,9,15,10,8,16,11,

%T 17,18,19,12,20,13,10,14,21,22,15,23,24,25,16,12,10,17,13,18,26,19,27,

%U 28,20,15,10,12,29,21,16,22,30,31,23,32,24,18,25,12,19,33

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

%F a(1)=1, for n>1, a(n) = A214370(n-1)+1.

%t mex[a_]:=Module[{q}, q=1; While[MemberQ[a,q] ,q++]; q]; a = Table[0,{k, 1, 100]}]; For[n=1, n<=100, n++, {If[a[[n]]==0, a[[n]] = mex[a]]; If[n>1, {nan = n+a[[n]]; If[(nan <= Length[a]) && (a[[nan]] == 0), a[[nan]] = a[[n]]]}]; }]; a

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

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

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

%Y Cf. A214370.

%Y Cf. A026242, A026338.

%K nonn,easy

%O 1,2

%A _Alex Ratushnyak_, Jul 14 2012

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Last modified September 18 13:51 EDT 2021. Contains 347527 sequences. (Running on oeis4.)