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A267304
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Earliest nonnegative increasing sequence having no 7-term subsequence with constant second differences.
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4
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0, 1, 2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 21, 24, 26, 28, 29, 31, 33, 35, 38, 40, 41, 43, 49, 50, 52, 53, 58, 59, 62, 63, 64, 69, 70, 72, 73, 77, 81, 82
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OFFSET
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1,3
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LINKS
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PROG
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(PARI) A267304(n, show=0, L=7, o=2, v=[0], D=v->v[2..-1]-v[1..-2])={ my(d, m); while( #v<n, show&&print1(v[#v]", "); v=concat(v, v[#v]); while( v[#v]++, forvec( i=vector(L, j, [if(j<L, j, #v), #v]), d=D(vecextract(v, i)); m=o; while(m--&&#Set(d=D(d))>1, ); #Set(d)>1||next(2), 2); break)); v[#v]} \\ M. F. Hasler, Jan 12 2016
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CROSSREFS
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Cf. A267305 (positive variant: starting with 1).
Cf. A240075 and A240555 for sequences avoiding 4-term subsequences with constant second differences.
Cf. A267300 and A267301 for sequences avoiding 5-term subsequences with constant second differences.
Cf. A267302 and A267303 for sequences avoiding 6-term subsequences with constant second differences.
Cf. A240556 and A240557 for sequences avoiding 5-term subsequences with constant third differences.
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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