This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A288847 #22 Jul 27 2017 09:53:33 %S A288847 217,255,446,558,717,735,775,945,958,1007,1062,1115,1269,1344,1503, %T A288847 1984,2215,2358,3003,3751,3858,4131,4471,5144,6174,6627,6915,6923, %U A288847 7033,7073,7139,7434,7530,7778,8125,8142,8239,8335,8575,8967,9186,9303,10040,10179,10856,11907,12081,12248 %N A288847 Numbers whose trajectories under the map x -> A230625(x) never reach a prime. %C A288847 Sequence suggested by _N. J. A. Sloane_ on the SeqFan mailing list. These are also the numbers n for which A230626(n) = -1 and A230627(n) = A287875(n) = 0. All currently-listed terms (those <= 3858) enter one of the two loops 1007 <-> 1269 and 1503 <-> 3751. %C A288847 Further values added (Jun 19 2017) based on _Sean A. Irvine_'s extension of the b-file for A230626. %e A288847 217, 255, 945, 1007 and 1269 are in the sequence because under the map x -> A230625(x): %e A288847 217 = 7*31 = binary 111*11111 -> binary 11111111 = 255 %e A288847 255 = 3*5*17 = binary 11*101*10001 -> binary 1110110001 = 945 %e A288847 945 = 3^3*5*7 = binary 11^11*101*111 -> binary 1111101111 = 1007 %e A288847 1007 = 19*53 = binary 10011*110101 -> binary 10011110101 = 1269 %e A288847 1269 = 3^3*47 = binary 11^11*101111 -> binary 1111101111 = 1007 %Y A288847 Cf. A230625, A230626, A230627, A287874, A287875, A287878. %K A288847 nonn,base %O A288847 1,1 %A A288847 _David J. Seal_, Jun 18 2017 %E A288847 a(43)-a(48) from _Chai Wah Wu_, Jul 13 2017