A293382 Decimal expansion of Sum_{n>=1} -(-1)^n * 2^n / (n * (2*3^n - 1)^n).

3, 9, 3, 0, 9, 7, 4, 9, 0, 7, 0, 0, 0, 8, 0, 5, 7, 6, 5, 4, 5, 3, 5, 4, 6, 1, 9, 8, 7, 3, 1, 2, 0, 8, 4, 5, 0, 2, 1, 3, 4, 1, 5, 7, 5, 0, 0, 6, 7, 5, 5, 7, 1, 0, 3, 2, 1, 9, 9, 0, 3, 0, 8, 0, 3, 2, 4, 7, 8, 8, 6, 7, 5, 3, 5, 7, 0, 7, 5, 7, 7, 4, 9, 8, 8, 6, 6, 3, 5, 5, 7, 6, 2, 2, 2, 4, 2, 3, 6, 9, 9, 7, 9, 5, 6, 4, 8, 7, 5, 4, 4, 9, 9, 3, 7, 8, 5, 0, 5, 9

Offset

0,1

Comments

This constant plus A293381 equals log(2), due to the identity:

Sum_{n=-oo..+oo, n<>0} (x - y^n)^n / n = -log(1-x), here x = 1/2, y = 1/3.

Links

Table of n, a(n) for n=0..119.

Formula

Constant: Sum_{n>=1} -(-1)^n * 2^n / (n * (2*3^n - 1)^n).

Constant: log(2) - Sum_{n>=1} (3^n - 2)^n / (n * 2^n * 3^(n^2)).

Example

Constant t = 0.3930974907000805765453546198731208450213415750067557103219903...
such that
t = 2/(2*3-1) - 2^2/(2*(2*3^2-1)^2) + 2^3/(3*(2*3^3-1)^3) - 2^4/(4*(2*3^4-1)^4) + 2^5/(5*(2*3^5-1)^5) - 2^6/(6*(2*3^6-1)^6) + 2^7/(7*(2*3^7-1)^7) - 2^8/(8*(2*3^8-1)^8) +...+ -(-1)^n * 2^n / (n * (2*3^n - 1)^n) +...
More explicitly,
t = 2/5 - 4/(2*17^2) + 8/(3*53^3) - 16/(4*161^4) + 32/(5*485^5) - 64/(6*1457^6) + 128/(7*4373^7) - 256/(8*13121^8) + 512/(9*39365^9) - 1024/(10*118097^10) +...
Also,
log(2) - t = (3 - 2)/(1*2*3) + (3^2 - 2)^2/(2*2^2*3^4) + (3^3 - 2)^3/(3*2^3*3^9) + (3^4 - 2)^4/(4*2^4*3^16) + (3^5 - 2)^5/(5*2^5*3^25) + (3^6 - 2)^6/(6*2^6*3^36) + (3^7 - 2)^7/(7*2^7*3^49) +...+ (3^n - 2)^n / (n * 2^n * 3^(n^2)) +...

Prog

(PARI) {t = suminf(n=1, -1.*(-1)^n * 2^n / (n * (2*3^n - 1)^n) )}
for(n=1, 120, print1(floor(10^n*t)%10, ", "))

Crossrefs

Cf. A002162, A293381, A292178, A292179, A293383, A293384.

Sequence in context: A098323 A225460 A305274 * A374242 A336501 A016674

Adjacent sequences: A293379 A293380 A293381 * A293383 A293384 A293385

Keyword

nonn,cons

Author

Paul D. Hanna, Oct 13 2017

Status

approved