A107048 Denominators of coefficients that satisfy: 2^n = Sum_{k=0..n} c(k)*x^k for n>=0, where c(k) = A107047(k)/a(k).

1, 1, 4, 108, 6912, 21600000, 2332800000, 1921161110400000, 31476303632793600000, 16727798278915463577600000, 209097478486443294720000000000

Offset

0,3

Links

Table of n, a(n) for n=0..10.

Formula

A107047(n)/a(n) = Sum_{k=0..n} T(n, k)*2^k where T(n, k) = A107045(n, k)/A107046(n, k) = [A079901^-1](n, k) (matrix inverse of A079901).

Example

2^0 = 1;
2^1 = 1 + 1;
2^2 = 1 + 1*2 + (1/4)*2^2;
2^3 = 1 + 1*3 + (1/4)*3^2 + (7/108)*3^3;
2^4 = 1 + 1*4 + (1/4)*4^2 + (7/108)*4^3 + (77/6912)*4^4.
Initial fractional coefficients are:
A107047/A107048 = {1, 1, 1/4, 7/108, 77/6912, 32387/21600000,
395159/2332800000, 31824093937/1921161110400000,
44855117331581/31476303632793600000, ... }.

Prog

(PARI) {a(n)=denominator(sum(k=0, n, 2^k*(matrix(n+1, n+1, r, c, if(r>=c, (r-1)^(c-1)))^-1)[n+1, k+1]))}

Crossrefs

Cf. A107047, A107045/A107046, A107049/A107050 (y=3), A107051/A107052 (y=4), A107053/A107054 (y=5).

Sequence in context: A024263 A090205 A061464 * A269187 A185702 A279046

Adjacent sequences: A107045 A107046 A107047 * A107049 A107050 A107051

Keyword

nonn,frac

Author

Paul D. Hanna, May 10 2005

Status

approved