cp's OEIS Frontend

A291788 Numbers n whose trajectory under the map k -> (psi(k)+phi(k))/2 (A291784) grows without limit.

%I A291788 #21 Jul 09 2025 04:45:12
%S A291788 45,48,50,55,56,60,68,69,70,72,74,75,76,77,78,80,84,85,86,87,88,90,91,
%T A291788 92,93,94,95,96,98,99,102,104,105,108,111,112,115,116,117,118,119,120,
%U A291788 122,123,124,126,133,134,135,136,140,141,142,143,144,145,146,147,152
%N A291788 Numbers n whose trajectory under the map k -> (psi(k)+phi(k))/2 (A291784) grows without limit.
%C A291788 See A291787 (where A291787(m) = 2*A291787(m-7) for m >= 35) for the trajectory of 45.
%C A291788 There is a similar proof that all the terms from 48 though 152 have a trajectory that merges with the trajectory of 45, and so doubles every 7 steps after a certain point. For example, the trajectory of 152 reaches 2^106*33 at step 390, is 2^107*33 at step 397, and thereafter doubles every 7 steps.- _N. J. A. Sloane_, Sep 24 2017
%Y A291788 Cf. A291784, A291785, A291786, A291787.
%K A291788 nonn,more
%O A291788 1,1
%A A291788 _N. J. A. Sloane_, Sep 03 2017, based on data supplied by _Hans Havermann_
%E A291788 Terms 104 to 152 added by _N. J. A. Sloane_, Sep 24 2017