A185578 - OEIS

A185578

Decimal expansion of Sum'_{m,n,p = -infinity .. infinity} (-1)^(m + n)/sqrt(m^2 + n^2 + p^2), negated.

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

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OFFSET

1,2

COMMENTS

The prime at the sum symbol means the term at m=n=p=0 is omitted.

LINKS

Table of n, a(n) for n=1..105.

Y. Sakamoto, Madelung constants of simple crystals expressed in terms of Born's basic potentials of 15 figures, J. Chem. Phys. 28 (1958) 164, variable Pi_3.

I. J. Zucker, Madelung constants and lattice sums for invariant cubic lattice complexes and certain tetragonal structures, J. Phys. A: Math. Gen. 8 (11) (1975) 1734, variable c(1).

I. J. Zucker, Functional equations for poly-dimensional zeta functions and the evaluation of Madelung constants, J. Phys. A: Math. Gen. 9 (4) (1976) 499, variable c(1).

FORMULA

Equals Pi/2 - 9*log(2)/2 + 4*Sum_{p>=1, n>=1} (1+(-1)^n+(-1)^(n+p))*cosech(d*Pi)/d where d = sqrt(n^2 + p^2).

EXAMPLE

1.48038980651222259790776170...

MATHEMATICA

digits = 105; Clear[f]; f[n_, p_] := f[n, p] = (s = Sqrt[n^2 + p^2]; ((1 + (-1)^n + (-1)^(n + p))*Csch[s*Pi])/s // N[#, digits+10]&); f[m_] := f[m] = Pi/2 - 9*Log[2]/2 + 4*Sum[f[n, p], {n, 1, m}, {p, 1, m}] // RealDigits[#, 10, digits + 10]& // First; f[0]; f[m=10]; While[ f[m] != f[m-10], Print[m]; m = m+10]; f[m][[1 ;; digits]] (* Jean-François Alcover, Feb 20 2013 *)

CROSSREFS

Cf. A185576, A185577, A185579, A185580, A185581, A185582, A185583.

Sequence in context: A245295 A135691 A011317 * A087264 A342995 A253191

Adjacent sequences: A185575 A185576 A185577 * A185579 A185580 A185581

KEYWORD

cons,nonn

AUTHOR

R. J. Mathar, Jan 31 2011

EXTENSIONS

More terms from Jean-François Alcover, Feb 20 2013

STATUS

approved