A288036 Numbers x such that the trajectory of x under the map x -> A090086(x) does not enter the cycle {14, 15}.

38, 39, 40, 220, 248, 508, 623, 662, 688, 723, 740, 742, 875, 898, 922, 950, 1078, 1103, 1130, 1179, 1208, 1262, 1312, 1390, 1598, 1600, 1635, 1652, 1678, 1780, 1787, 2027, 2198, 2319, 2378, 2380, 2495, 2547, 2560, 2588, 2770, 2775, 2900, 2950, 2963, 3003

Offset

1,1

Links

Table of n, a(n) for n=1..46.

Example

The trajectory of 220 enters the cycle {38, 39} after one step, so 220 is a term of the sequence.

Mathematica

Select[Range@ 3000, Function[k, ! MemberQ[NestWhileList[Function[n, Block[{j = 1}, While[GCD[n, j] > 1 || PrimeQ@ j || PowerMod[n, j - 1, j] != 1, i = j++]; j]], k, # != 15 &, 1, 100], 15]]] (* Michael De Vlieger, Jun 06 2017, after Robert G. Wilson v at A090086 *)

Prog

(PARI) a090086(n) = forcomposite(c=1, , if(Mod(n, c)^(c-1)==1, return(c)))
trajectory(n, terms) = my(v=[n]); while(#v < terms, v=concat(v, a090086(v[#v]))); v
is(n) = my(len=2, t=trajectory(n, len), k=#t); while(1, k--; if(t[k]==t[#t], if(t[#t]!=14 && t[#t]!=15, return(1), return(0))); if(k==1, len++; t=trajectory(n, len); k=#t))

Crossrefs

Cf. A090086.

Sequence in context: A165859 A341708 A031958 * A350854 A272035 A056027

Adjacent sequences: A288033 A288034 A288035 * A288037 A288038 A288039

Keyword

nonn

Author

Felix Fröhlich, Jun 04 2017

Status

approved