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A002790 Denominators of Cauchy numbers of second type (= Bernoulli numbers B_n^{(n)}).

%I A002790 M1559 N0608 #120 Aug 19 2025 03:41:09
%S A002790 1,2,6,4,30,12,84,24,90,20,132,24,5460,840,360,16,1530,180,7980,840,
%T A002790 13860,440,1656,720,81900,6552,216,112,3480,240,114576,7392,117810,
%U A002790 2380,1260,72,3838380,207480,32760,560,568260,27720,238392,55440,869400,2576,236880
%N A002790 Denominators of Cauchy numbers of second type (= Bernoulli numbers B_n^{(n)}).
%C A002790 The numerators are given in A002657.
%C A002790 These coefficients (with alternating signs) are also known as the Nørlund [or Norlund, Noerlund or Nörlund] numbers.
%C A002790 A simple series with the signless Cauchy numbers of second type C2(n) leads to Euler's constant: gamma = 1 - Sum_{n >=1} C2(n)/(n*(n+1)!) = 1 - 1/4 - 5/72 - 1/32 - 251/14400 - 19/1728 - 19087/2540160 - ..., see references [Blagouchine] below, as well as A075266 and A262235. - _Iaroslav V. Blagouchine_, Sep 15 2015
%C A002790 a(n) appears to be divisible by n+1. - _Hal M. Switkay_, Aug 15 2025
%D A002790 L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 294.
%D A002790 L. M. Milne-Thompson, Calculus of Finite Differences, 1951, p. 136.
%D A002790 N. E. Nørlund, Vorlesungen über Differenzenrechnung, Springer-Verlag, Berlin, 1924.
%D A002790 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
%D A002790 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A002790 T. D. Noe, <a href="/A002790/b002790.txt">Table of n, a(n) for n = 0..1000</a>
%H A002790 Ibrahim M. Alabdulmohsin, <a href="https://doi.org/10.1007/978-3-319-74648-7_7">The Language of Finite Differences</a>, in Summability Calculus: A Comprehensive Theory of Fractional Finite Sums, Springer, Cham, pp 133-149.
%H A002790 Iaroslav V. Blagouchine, <a href="http://dx.doi.org/10.1016/j.jmaa.2016.04.032">Two series expansions for the logarithm of the gamma function involving Stirling numbers and containing only rational coefficients for certain arguments related to 1/pi</a>, Journal of Mathematical Analysis and Applications (Elsevier), 2016. <a href="http://arxiv.org/abs/1408.3902">arXiv version</a>, arXiv:1408.3902 [math.NT], 2014-2016.
%H A002790 Iaroslav V. Blagouchine, <a href="http://dx.doi.org/10.1016/j.jnt.2015.06.012">Expansions of generalized Euler's constants into the series of polynomials in 1/pi^2 and into the formal enveloping series with rational coefficients only.</a> Journal of Number Theory (Elsevier), vol. 158, pp. 365-396, 2016. <a href="http://arxiv.org/abs/1501.00740">arXiv version</a>, arXiv:1501.00740 [math.NT], 2015.
%H A002790 Iaroslav V. Blagouchine, <a href="http://math.colgate.edu/~integers/sjs3/sjs3.Abstract.html">Three notes on Ser's and Hasse's representation for the zeta-functions</a>, Integers (2018) 18A, Article #A3.
%H A002790 C. H. Karlson & N. J. A. Sloane, <a href="/A002790/a002790.pdf">Correspondence, 1974</a>
%H A002790 Guodong Liu, <a href="https://web.archive.org/web/2024*/https://www.fq.math.ca/Papers1/45-2/quartliu02_2007.pdf">Some computational formulas for Norlund numbers</a>, Fib. Quart., 45 (2007), 133-137.
%H A002790 Guo-Dong Liu, H. M. Srivastava, Hai-Quing Wang, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL17/Srivastava/sriva3.html">Some Formulas for a Family of Numbers Analogous to the Higher-Order Bernoulli Numbers</a>, J. Int. Seq. 17 (2014) # 14.4.6.
%H A002790 Rui-Li Liu and Feng-Zhen Zhao, <a href="https://hosted.math.rochester.edu/ojac/vol14/183.pdf">Log-concavity of two sequences related to Cauchy numbers of two kinds</a>, Online Journal of Analytic Combinatorics, Issue 14 (2019), #09.
%H A002790 Donatella Merlini, Renzo Sprugnoli and M. Cecilia Verri, <a href="http://dx.doi.org/10.1016/j.disc.2006.03.065">The Cauchy numbers</a>, Discrete Math. 306 (2006), no. 16, 1906-1920.
%H A002790 L. M. Milne-Thompson, <a href="/A002657/a002657.pdf"> Calculus of Finite Differences</a>, 1951. [Annotated scan of pages 135, 136 only]
%H A002790 N. E. Nørlund, <a href="http://www-gdz.sub.uni-goettingen.de/cgi-bin/digbib.cgi?PPN373206070">Vorlesungen ueber Differenzenrechnung</a> Springer 1924, p. 461.
%H A002790 N. E. Nörlund, <a href="/A001896/a001896_1.pdf">Vorlesungen über Differenzenrechnung</a>, Springer-Verlag, Berlin, 1924; page 461 [Annotated scanned copy of pages 144-151 and 456-463]
%H A002790 Feng-Zhen Zhao, <a href="http://dx.doi.org/10.1016/j.disc.2008.10.013">Sums of products of Cauchy numbers</a>, Discrete Math., 309 (2009), 3830-3842.
%H A002790 <a href="/index/Be#Bernoulli">Index entries for sequences related to Bernoulli numbers.</a>
%F A002790 Denominator of integral of x(x+1)...(x+n-1) from 0 to 1.
%F A002790 E.g.f.: -x/((1-x)*log(1-x)). - Corrected by _Iaroslav V. Blagouchine_, May 07 2016.
%F A002790 Denominator of Sum_{k=0..n} (-1)^k A008275(n,k)/(k+1). - _Peter Luschny_, Apr 28 2009
%F A002790 a(n) = denominator(n!*v(n)), where v(n) = 1 - Sum_{i=0..n-1} v(i)/(n-i+1), v(0)=1. - _Vladimir Kruchinin_, Aug 28 2013
%e A002790 1, 1/2, 5/6, 9/4, 251/30, 475/12, 19087/84, 36799/24, 1070017/90, ...
%p A002790 A002790 := proc(n)
%p A002790     denom(add((-1)^k*Stirling1(n, k)/(k+1), k=0..n)) ;
%p A002790 end proc: # _Peter Luschny_, Apr 28 2009
%p A002790 v := proc(n) option remember; ifelse(n=0, 1, 1 - add(v(i)/(n-i+1), i=0..n-1)) end:
%p A002790 seq(denom(n!*v(n)), n = 0..46); # after _Vladimir Kruchinin_, _Peter Luschny_, Aug 17 2025
%t A002790 Table[ Denominator[ NorlundB[n, n]], {n, 0, 60}] (* _Vladimir Joseph Stephan Orlovsky_, Dec 30 2010 *)
%o A002790 (Maxima)
%o A002790 v(n):=if n=0 then 1 else 1-sum(v(i)/(n-i+1),i,0,n-1);
%o A002790 makelist(denom(n!*v(n)),n,0,10); /* _Vladimir Kruchinin_, Aug 28 2013 */
%o A002790 (Magma) m:=60; R<x>:=PowerSeriesRing(Rationals(), m); b:=Coefficients(R!(-x/((1-x)*Log(1-x)) )); [Denominator(Factorial(n-1)*b[n]): n in [1..m-1]]; // _G. C. Greubel_, Oct 28 2018
%Y A002790 Cf. A002657, A075266, A075267, A262235.
%Y A002790 See also A002208, A002209, A002206, A002207, A006232, A006233.
%K A002790 nonn,frac,nice,easy,changed
%O A002790 0,2
%A A002790 _N. J. A. Sloane_