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%I A258987 #21 Jun 06 2025 08:37:15
%S A258987 2,1,3,7,9,8,8,6,8,2,2,4,5,9,2,5,4,7,0,9,9,5,8,3,5,7,4,5,0,8,0,3,3,6,
%T A258987 4,9,6,4,0,9,5,8,9,5,7,8,6,5,5,1,7,5,5,6,1,4,4,5,1,2,7,4,8,9,4,7,1,2,
%U A258987 5,8,3,6,6,1,4,6,9,8,1,0,2,0,4,1,7,0,9,5,6,0,2,8,9,9,9,1,1,5,5,0,6,4,8
%N A258987 Decimal expansion of the multiple zeta value (Euler sum) zetamult(3,3).
%H A258987 Eric Weisstein's MathWorld, <a href="https://mathworld.wolfram.com/MultivariateZetaFunction.html">Multivariate Zeta Function</a>
%H A258987 Wikipedia, <a href="https://en.wikipedia.org/wiki/Multiple_zeta_function">Multiple zeta function</a>
%H A258987 <a href="/wiki/Index_to_constants#Start_of_section_M">Index to constants which are multiple zeta values</a> (3,3)
%F A258987 zetamult(3,3) = Sum_{m>=2} (Sum_{n=1..m-1} 1/(m^3*n^3)) = (1/2)*zeta(3)^2 - (1/2)*zeta(6). - [Corrected by _Detlef Meya_, Jun 06 2025 ]
%e A258987 0.213798868224592547099583574508033649640958957865517556144512748947...
%t A258987 RealDigits[(1/2)*Zeta[3]^2 - (1/2)*Zeta[6], 10, 103] // First (* Corrected by _Detlef Meya_, Jun 06 2025 *)
%o A258987 (PARI) zetamult([3,3]) \\ _Charles R Greathouse IV_, Jan 21 2016
%Y A258987 Cf. A072691 (zetamult(1,1)), A197110 (zetamult(2,2)), A258983 (zetamult(3,2)), A258984 (4,2), A258985 (5,2), A258947 (6,2), A258986 (2,3), A258988 (4,3), A258982 (5,3), A258989 (2,4), A258990 (3,4), A258991 (4,4).
%K A258987 nonn,cons,easy
%O A258987 0,1
%A A258987 _Jean-François Alcover_, Jun 16 2015