cp's OEIS Frontend

A100480 a(1)=1 and, for n>1, a(n) is the smallest positive integer such that the subset S(c) of {1,2,3,...,n} defined by S(c)={k|1<=k<=n; a(k)=c} does not contain a 3-term arithmetic progression for any integer c.

%I A100480 #18 Jun 28 2022 10:58:04
%S A100480 1,1,2,1,1,2,2,3,3,1,1,2,1,1,2,2,3,3,2,3,3,4,4,5,4,4,5,1,1,2,1,1,2,2,
%T A100480 3,3,1,1,2,1,1,2,2,3,3,2,3,3,4,4,5,4,4,5,2,3,3,4,4,5,4,4,5,5,6,6,5,6,
%U A100480 6,7,7,8,5,6,6,5,6,6,7,7,8,1,1,2,1,1,2,2,3,3,1,1,2,1,1,2,2,3,3,2,3,3,4,4,5
%N A100480 a(1)=1 and, for n>1, a(n) is the smallest positive integer such that the subset S(c) of {1,2,3,...,n} defined by S(c)={k|1<=k<=n; a(k)=c} does not contain a 3-term arithmetic progression for any integer c.
%C A100480 The sequence of values of n for which a(n)=1 is given by {A005836(i)-1}.
%H A100480 Samuel B. Reid, <a href="/A100480/b100480.txt">Table of n, a(n) for n = 1..10000</a>
%H A100480 Samuel B. Reid, <a href="/A100480/a100480.py.txt">Python program for A100480</a>
%F A100480 a(n + 1) = A006997(n) + 1 for any n >= 0. - _Rémy Sigrist_, Jun 28 2022
%o A100480 (Python) # See Links section.
%Y A100480 Cf. A005836, A006997, A135415, A229037.
%K A100480 nonn
%O A100480 1,3
%A A100480 _John W. Layman_, Nov 22 2004