login
Mean of the first 2^n nonnegative powers of 3, i.e., (1 + 3 + 3^2 + ... + 3^(2^n-1))/2^n.
8

%I #15 Oct 20 2024 23:48:06

%S 1,2,10,410,1345210,28953440450810,26825654846035253786389446010,

%T 46055408506791340513753409614892651037805514032327504332410

%N Mean of the first 2^n nonnegative powers of 3, i.e., (1 + 3 + 3^2 + ... + 3^(2^n-1))/2^n.

%H Harry J. Smith, <a href="/A059723/b059723.txt">Table of n, a(n) for n = 0..11</a>

%H N. J. A. Sloane, <a href="https://www.youtube.com/watch?v=3RAYoaKMckM">A Nasty Surprise in a Sequence and Other OEIS Stories</a>, Experimental Mathematics Seminar, Rutgers University, Oct 10 2024, Youtube video; <a href="https://sites.math.rutgers.edu/~zeilberg/expmath/sloane85BD.pdf">Slides</a> [Mentions this sequence]

%F a(n) = (3^(2^n) - 1)/2^(n+1).

%e a(3) = (1 + 3 + 9 + 27 + 81 + 243 + 729 + 2187)/8 = 3280/8 = 410.

%o (PARI) { for (n=0, 11, write("b059723.txt", n, " ", (3^(2^n) - 1)/2^(n + 1)); ) } \\ _Harry J. Smith_, Jun 28 2009

%Y Cf. A059721, A059722.

%K nonn

%O 0,2

%A _Henry Bottomley_, Feb 07 2001