A008345 a(n+1) = a(n)-b(n+1) if a(n) >= b(n+1) else a(n)+b(n+1), where {b(n)} are the triangular numbers A000217.

0, 1, 4, 10, 0, 15, 36, 8, 44, 89, 34, 100, 22, 113, 8, 128, 264, 111, 282, 92, 302, 71, 324, 48, 348, 23, 374, 752, 346, 781, 316, 812, 284, 845, 250, 880, 214, 917, 176, 956, 136, 997, 94, 1040, 50, 1085, 4, 1132, 2308, 1083, 2358, 1032, 2410, 979, 2464, 924

Offset: 0

Author

N. J. A. Sloane and J. H. Conway

Keywords

• nonn
• easy

Comments

a(0) and a(4) are both zero. Are there any other zero values? - N. J. A. Sloane, Sep 12 2019

Links

• Rémy Sigrist, Table of n, a(n) for n = 0..25000 (first 1001 terms from Franklin T. Adams-Watters)

Crossrefs

Cf. A000217, A008344, A076042.

Programs

Maple

A008345 := proc(n) option remember; if n = 1 then n-1 elif A008345(n-1) >= n*(n+1)/2 then A008345(n-1)-n*(n+1)/2 else A008345(n-1)+n*(n+1)/2; fi; end;

Mathematica

nxt[{n_,a_}]:=Module[{tr=((n+1)(n+2))/2},{n+1,If[a>=tr,a-tr,a+tr]}]; Transpose[NestList[nxt,{0,0},50]][[2]] (* Harvey P. Dale, Jun 19 2013 *)