This site is supported by donations to The OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A240557 Earliest positive increasing sequence with no 5-term subsequence of constant third differences. 12
 1, 2, 3, 4, 6, 8, 12, 16, 17, 28, 48, 49, 65, 96, 176, 197, 212, 213, 215, 248, 250, 253, 399, 840, 1003, 1015, 1017, 1036, 1037, 1038, 1052, 1055, 1073, 1122, 1144, 1147, 1173, 1259, 4272, 4283, 4285, 4337, 4572, 4579, 4583, 4599, 4614, 4623, 4629, 4647 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS For the nonnegative sequence, see A240556, which is this sequence minus 1. Is there a simple way of determining this sequence, as in the case of the no 3-term arithmetic progression? See crossreferences for sequences avoiding arithmetic progressions. - M. F. Hasler, Jan 12 2016 LINKS MATHEMATICA t = {1, 2, 3, 4}; Do[s = Table[Append[i, n], {i, Subsets[t, {4}]}]; If[! MemberQ[Flatten[Table[Differences[i, 4], {i, s}]], 0], AppendTo[t, n]], {n, 5, 5000}]; t PROG (PARI) A240557(n, show=0, L=5, o=3, v=[1], D=v->v[2..-1]-v[1..-2])={ my(d, m); while( #v1, ); #Set(d)>1||next(2), 2); break)); v[#v]} \\ M. F. Hasler, Jan 12 2016 CROSSREFS Cf. A240556 (starting with 0). No 3-term AP: A005836 (>=0), A003278 (>0); no 4-term AP: A240075 (>=0), A240555 (>0); no 5-term AP: A020654 (>=0), A020655 (>0); no 6-term AP: A020656 (>=0), A005838 (>0); no 7-term AP: A020657 (>=0), A020658 (>0); no 8-term AP: A020659 (>=0), A020660 (>0); no 9-term AP: A020661 (>=0), A020662 (>0); no 10-term AP: A020663 (>=0), A020664 (>0). Cf. A240075 and A240555 for sequences avoiding 4-term subsequences with constant second differences. Sequence in context: A187448 A321266 A018662 * A326712 A191612 A048874 Adjacent sequences:  A240554 A240555 A240556 * A240558 A240559 A240560 KEYWORD nonn AUTHOR T. D. Noe, Apr 09 2014 EXTENSIONS Definition corrected by M. F. Hasler, Jan 12 2016 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified October 20 10:41 EDT 2019. Contains 328257 sequences. (Running on oeis4.)