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 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. 2
 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, 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, 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 COMMENTS The sequence of values of n for which a(n)=1 is given by {A005836(i)-1}. LINKS Samuel B. Reid, Table of n, a(n) for n = 1..10000 Samuel B. Reid, Python program for A100480 FORMULA a(n + 1) = A006997(n) + 1 for any n >= 0. - Rémy Sigrist, Jun 28 2022 PROG (Python) # See Links section. CROSSREFS Cf. A005836, A006997, A135415, A229037. Sequence in context: A029333 A029261 A359384 * A268811 A351192 A306460 Adjacent sequences: A100477 A100478 A100479 * A100481 A100482 A100483 KEYWORD nonn AUTHOR John W. Layman, Nov 22 2004 STATUS approved

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Last modified March 22 11:07 EDT 2023. Contains 361423 sequences. (Running on oeis4.)