A033158 Begins with (1, 5); avoids 3-term arithmetic progressions.

1, 5, 6, 8, 12, 13, 17, 24, 27, 32, 34, 38, 39, 45, 50, 57, 74, 79, 81, 86, 96, 100, 107, 125, 129, 132, 137, 144, 170, 189, 198, 204, 221, 222, 227, 228, 239, 248, 260, 270, 277, 285, 288, 303, 309, 311, 314, 320, 338, 386, 393, 398, 423, 435, 456, 467, 471, 492, 494, 500

Offset

1,2

References

Iacobescu, F. 'Smarandache Partition Type and Other Sequences.' Bull. Pure Appl. Sci. 16E, 237-240, 1997.

H. Ibstedt, A Few Smarandache Sequences, Smarandache Notions Journal, Vol. 8, No. 1-2-3, 1997, 170-183.

Links

Alois P. Heinz, Table of n, a(n) for n = 1..2000

Eric Weisstein's World of Mathematics, Nonarithmetic Progression Sequence

Mathematica

ss[s1_, M_] := Module[{n, chvec, swi, p, s2, i, j, t1, mmm}, t1 = Length[s1]; mmm = 1000; s2 = Table[s1, {t1 + M}] // Flatten; chvec = Array[0 &, mmm]; For[i = 1, i <= t1, i++, chvec[[s2[[i]]]] = 1]; (* get n-th term *) For[n = t1 + 1, n <= t1 + M, n++, (* try i as next term *) For[i = s2[[n - 1]] + 1, i <= mmm, i++, swi = -1; (* test against j-th term *) For[j = 1, j <= n - 2, j++, p = s2[[n - j]]; If[2*p - i < 0, Break[]]; If[chvec[[2*p - i]] == 1, swi = 1; Break[]]]; If[swi == -1, s2[[n]] = i; chvec[[i]] = 1; Break[]]]; If[swi == 1, Print["Error, no solution at n = ", n]]]; Table[s2[[i]], {i, 1, t1 + M}]]; A033158 = ss[{0, 4}, 80] + 1 (* Jean-François Alcover, Oct 08 2013, after Maple program in A185256 *)

Crossrefs

Equals A005487(n-1)+1.

Sequence in context: A048583 A169622 A047321 * A193569 A032721 A105106

Adjacent sequences: A033155 A033156 A033157 * A033159 A033160 A033161

Keyword

nonn

Author

N. J. A. Sloane.

Status

approved