A092324 Values m_0 = 0, m_1, m_2, ... associated with divergent series T shown below.

0, 227, 22945, 273604248, 1506633655224, 980847385203985367, 294892816889532972106622, 10481800650337122455198767414397, 172058676801196585230804191607100491062

Offset

0,2

Comments

T = 1

- (1/2 + 1/4 + 1/6 + ... + 1/(2m_1))

+ (1/3 + 1/5 + 1/7 + ... + 1/(2m_2+1))

- (1/(2m_1+2) + 1/(2m_1+4) + ... + 1/(2m_3)

+ (1/(2m_2+3) + 1/(2m_2+5) + ... + 1/(2m_4+1))

- (1/(2m_3+2) + 1/(2m_3+4) + ... + 1/(2m_5)

+ (1/(2m_4+3) + 1/(2m_4+5) + ... + 1/(2m_6+1))

- ...

where the partial sums of the terms from 1 through the end of rows 0, 1, ... are respectively 1, just < -2, just > 3, just < -4, just > 5, etc.

Every positive number appears exactly once as a denominator in T.

The series T is a divergent rearrangement of the conditionally convergent series Sum_{j>=1} (-1)^j/j which has the entire real number system as its set of limit points.

Comment from Hans Havermann: I calculated these with Mathematica. I used NSum[1/(2i), {i, 1, x}] for the even denominators, where I had to adjust the options to obtain maximal accuracy and N[(EulerGamma + Log[4] - 2)/2 + PolyGamma[0, 3/2 + y]/2, precision] for the odd denominators. The precision needed for the last term shown was around 45 digits.

References

B. R. Gelbaum and J. M. H. Olmsted, Counterexamples in Analysis, Holden-Day, San Francisco, 1964; see p. 55.

Links

Table of n, a(n) for n=0..8.

Example

1 - (1/2 + 1/4 + 1/6 + ... + 1/454) = -2.002183354..., which is just less than -2; so a(1) = m_1 = 227.
1 - (1/2 + 1/4 + 1/6 + ... + 1/454) + (1/3 + 1/5 + ... + 1/45891) = 3.000021113057..., which is just greater than 3; so a(2) = m_2 = 22945.

Crossrefs

Cf. A092267 (essentially the same), A002387, A056053, A092318, A092317, A092315.

Cf. A092273.

Sequence in context: A349985 A209843 A115998 * A122976 A098245 A343169

Adjacent sequences: A092321 A092322 A092323 * A092325 A092326 A092327

Keyword

nonn,nice

Author

N. J. A. Sloane, Feb 16 2004

Extensions

a(2) and a(3) from Hugo Pfoertner, Feb 17 2004

a(4) onwards from Hans Havermann, Feb 18 2004

Status

approved