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 A095385 #9 Jun 05 2025 06:34:28
%S A095385 4,72,180,192,228,240,312,600,1092,1152,1428,1488,1608,1620,1872,2088,
%T A095385 2112,2592,2688,3000,3168,3252,3360,3528,4272,4548,4800,5640,6552,
%U A095385 6960,7488,7560,8088,8292,8388,8820,9000,9012,9240,9768,10008,10068,10272
%N A095385 Numbers k with property that k is a peak value in 3x+1 trajectory such that both k+1 and k-1 are prime numbers.
%C A095385 In such cases it seems that initial value equals peak value. Proof needed!
%e A095385 k=72: list={72,36,18,9,28,14,7,22,11,34,17,52,26,13,40,20,10,5,16,8,4,2,1}
%t A095385 c[x_]:=c[x]=(1-Mod[x, 2])*(x/2)+Mod[x, 2]*(3*x+1);c[1]=1; fpl[x_]:=FixedPointList[c, x]; {$RecursionLimit=1000;m=0}; Do[If[PrimeQ[1+Max[fpl[n]]]&&PrimeQ[ -1+Max[fpl[n]]], Print[n]], {n, 1, 10000}]
%Y A095385 Intersection of A014574 and A025586.
%K A095385 nonn
%O A095385 1,1
%A A095385 _Labos Elemer_, Jun 14 2004