A132425 - OEIS

A132425

a(1)=1. a(2)=2. For n >= 3, a(n) is the smallest integer which is > a(n-1), is not coprime to a(n-1) and is such that a(n)-a(n-1) does not equal a(m)-a(m-1) for any m < n.

%I #9 Sep 16 2015 13:57:28

%S 1,2,4,8,14,21,24,32,42,51,63,77,88,104,117,132,150,155,175,196,218,

%T 242,268,296,326,358,392,427,469,518,554,592,629,646,665,690,713,744,

%U 771,804,843,888,928,957,1001,1053,1101,1152,1198,1248,1302,1358,1416,1473

%N a(1)=1. a(2)=2. For n >= 3, a(n) is the smallest integer which is > a(n-1), is not coprime to a(n-1) and is such that a(n)-a(n-1) does not equal a(m)-a(m-1) for any m < n.

%C Is {a(n+1)-a(n)} a permutation of the positive integers?

%t a = {1, 2}; For[n = 1, n < 1500, n++, n = a[[ -1]]; c = 0; While[c == 0, n++; If[GCD[n, a[[ -1]]] > 1, b = 0; For[j = 1, j < Length[a], j++, If[a[[j + 1]] - a[[j]] == n - a[[ -1]], b = 1]]; If[b == 0, AppendTo[a, n]; c = 1]]]]; a (* _Stefan Steinerberger_, Oct 21 2007 *)

%Y Cf. A089781, A132426.

%K nonn

%O 1,2

%A _Leroy Quet_, Aug 20 2007

%E More terms from _Stefan Steinerberger_, Oct 21 2007