cp's OEIS Frontend

A387486 Numbers x such that there exist four integers y, z, t and w with x<=y<=z<=t<=w such that psi(x) = psi(y) = psi(z) = psi(t) = psi(w) = (x + y + z + t + w)/4.

%I A387486 #12 Sep 04 2025 10:52:57
%S A387486 4,6,8,12,28,30,32,36,40,44,45,78,84,98,104,112,124,140,158,174,176,
%T A387486 180,192,196,198,200,204,216,220,225,230,232,236,238,254,260,272,276,
%U A387486 284,300,304,310,320,332,340,342,348,350,354,357,360,364,368,374,378,380
%N A387486 Numbers x such that there exist four integers y, z, t and w with x<=y<=z<=t<=w such that psi(x) = psi(y) = psi(z) = psi(t) = psi(w) = (x + y + z + t + w)/4.
%C A387486 The numbers x, y, z, t and w form a psi-amicable quintuple.
%H A387486 S. I. Dimitrov, <a href="https://arxiv.org/abs/2508.02318">On psi-amicable numbers and their generalizations</a>, arXiv:2508.02318 [math.NT], 2025.
%e A387486 200 is in the sequence since psi(200) = psi(267) = psi(295) = psi(319) = psi(359) = 360 = (200 + 267 + 295 + 319 + 359)/4.
%Y A387486 Cf. A001615, A385852, A387291, A387292.
%K A387486 nonn,easy,new
%O A387486 1,1
%A A387486 _S. I. Dimitrov_, Aug 31 2025