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 A263026 a(n) = Sum_{k=1..n} stirling2(n,k)*((k+1)!)^3)/8. 1
 1, 28, 1810, 226558, 48859606, 16717044358, 8536211225830, 6206816010688678, 6191950081736354086, 8223501207813329312038, 14182148054223247947725350, 31102596462109513014876988198, 85207893723061275473574262742566, 287156553366174285430392015701185318, 1174632657911183483067648902342293048870 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS FORMULA Representation as a sum of infinite series of special values of Meijer G functions, a(n) = (1/8) Sum_{k>=0} MeijerG([[1-k],[]],[[2,2,2],[]],1)) k^n/k!. The Meijer G functions in the above formula cannot be represented through any other special function. MAPLE # This program is intended for quick evaluation of a(n) with(combinat): a:= n-> add(stirling2(n, k)*((k+1)!)^3, k=1..n)/8: seq(a(n), n=1..15); # Maple program for the evaluation and verification of the infinite series representation: a:= n-> evalf(sum(k^n*evalf(MeijerG([[1-k], []], [[2, 2, 2], []], 1))/k!, k=0..infinity)/8); # n=1, 2, ... . # This infinite series is slowly converging and the use of above formula will presumably not give the result in a reasonable time. Instead it is practical to replace the upper summation limit k = infinity by some kmax, say kmax = 6000. For example this yields  for a(4) = 226558 the approximation 226557.9980714 in about 100 sec. Increasing kmax improves this approximation. MATHEMATICA Table[Sum[StirlingS2[n, k] ((k + 1)!)^3/8, {k, n}], {n, 15}] (* Michael De Vlieger, Oct 09 2015 *) CROSSREFS Cf. A261833, A262960. Sequence in context: A182400 A333125 A197438 * A294192 A202811 A285749 Adjacent sequences:  A263023 A263024 A263025 * A263027 A263028 A263029 KEYWORD nonn AUTHOR Karol A. Penson and Katarzyna Gorska, Oct 08 2015 STATUS approved

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Last modified June 18 22:37 EDT 2021. Contains 345125 sequences. (Running on oeis4.)