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 A287319 #15 May 24 2017 05:29:30 %S A287319 1,3,151,26512143,318400215865581346424671, %T A287319 1240913164837493520914469575281720548839055905624577375251388717505927743 %N A287319 Smallest number k which becomes a power of 2 after being transformed by the reduced Collatz function k=(3*k+1)/2 precisely n times. %C A287319 a(7) is too large to include. %C A287319 I conjecture that all members of a(n) are members of A054646 and A010120, "Smallest number to give 2^(2n) in a hailstone (3x + 1) sequence" and "Smallest start for a `3x+1' sequence containing 2^n". %F A287319 a(n) = ((2^(3^(n-1)+n)-3^n+2^n))/3^n. %e A287319 For n = 3, the reduced Collatz sequence k = (3*k+1)/2 is 151, 227, 341, 512. %Y A287319 Cf. A054646 and A010120. %K A287319 nonn %O A287319 1,2 %A A287319 _Joe Slater_, May 23 2017