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a(1) = 1; for n > 1, a(n) = a(n-1)-(n+1) if this is positive and has not already appeared in the sequence, otherwise a(n) = a(n-1)+(n+1).
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%I #24 May 08 2021 23:05:05

%S 1,4,8,3,9,2,10,19,29,18,6,19,5,20,36,53,35,16,36,15,37,14,38,13,39,

%T 12,40,11,41,72,104,71,105,70,34,71,33,72,32,73,31,74,30,75,121,168,

%U 120,169,119,68,120,67,121,66,122,65,7,66,126,187,125,62,126,61,127,60,128

%N a(1) = 1; for n > 1, a(n) = a(n-1)-(n+1) if this is positive and has not already appeared in the sequence, otherwise a(n) = a(n-1)+(n+1).

%H Indranil Ghosh, <a href="/A066199/b066199.txt">Table of n, a(n) for n = 1..10000</a>

%H <a href="/index/Rea#Recaman">Index entries for sequences related to Recamán's sequence</a>

%o (Python)

%o l=[0, 1]

%o for n in range(2, 101):

%o x=l[n - 1] - (n + 1)

%o if x>0 and x not in l: l.append(x)

%o else: l.append(l[n - 1] + (n + 1))

%o print(l[1:]) # _Indranil Ghosh_, Jun 02 2017

%Y A variant of A005132. A row of the array in A066201.

%K nonn,easy

%O 1,2

%A _N. J. A. Sloane_, Dec 16 2001

%E More terms from _Sascha Kurz_, Mar 24 2002