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Increasing sequence: "if n appears a*n+b does not", case a(1)=4, a=2, b=1.
4

%I #2 Mar 30 2012 17:26:21

%S 4,5,6,7,8,10,12,14,16,18,19,20,22,23,24,26,27,28,30,31,32,34,35,36,

%T 38,40,42,43,44,46,48,50,51,52,54,56,58,59,60,62,64,66,67,68,70,72,74,

%U 75,76,78,79,80,82,83,84,86,88,90,91,92,94,95,96,98,99,100

%N Increasing sequence: "if n appears a*n+b does not", case a(1)=4, a=2, b=1.

%t s={4};With[{a=2,b=1},Do[If[FreeQ[s,(n-b)/a],AppendTo[s,n]],{n,5,100}]];s

%Y Cf. A121538, A121539, A121540, A121542.

%K nonn

%O 1,1

%A _Zak Seidov_, Aug 08 2006