Search: id:A002775
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%I A002775 M4540 N1927
%S A002775 0,1,8,54,384,3000,25920,246960,2580480,29393280,362880000,4829932800,
               68976230400,
%T A002775 1052366515200,17086945075200,294226732800000,5356234211328000,102793666719744000,
%U A002775 2074369080655872000,43913881247588352000,973160803270656000000,22531105497723863040000
%N A002775 n^2*n!.
%C A002775 Contribution from Johannes W. Meijer (meijgia(AT)hotmail.com), Oct 16 
               2009: (Start)
%C A002775 Denominators in power series expansion of the higher order exponential 
               integral E(x,m=2,n=1) - (gamma^2/2 + Pi^2/12 + gamma*ln(x) + ln(x)^2/
               2), n>0, see A163931.
%C A002775 (End)
%D A002775 N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, 
               Academic Press, 1995 (includes this sequence).
%D A002775 N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 
               (includes this sequence).
%D A002775 J. D. H. Dickson, Discussion of two double series arising from the number 
               of terms in determinants of certain forms, Proc. London Math. Soc., 
               10 (1879), 120-122.
%F A002775 E.g.f.: x*(1+x)/(1-x)^3. - Vladeta Jovovic (vladeta(AT)eunet.rs), Dec 
               01 2002
%F A002775 Sum of all matrix elements M(i, j) = i/(i+j) multiplied by 2*n!. a(n) 
               = 2*n! * Sum[Sum[i/(i+j), {i, 1, n}], {j, 1, n}] Example: a(2) = 
               2*2! * (1/(1+1) + 1/(1+2) + 2/(2+1) + 2/(2+2)) = 8 - Alexander Adamchuk 
               (alex(AT)kolmogorov.com), Oct 24 2004
%p A002775 with(combinat):for n from 0 to 15 do printf(`%d, `,n!/2*sum(2*n, k=1..n)) 
               od: - Zerinvary Lajos (zerinvarylajos(AT)yahoo.com), Mar 13 2007
%p A002775 seq(sum(sum(mul(k, k=1..n),l=1..n),m=1..n), n=0..21); - Zerinvary Lajos 
               (zerinvarylajos(AT)yahoo.com), Jan 26 2008
%p A002775 with (combstruct):a:=proc(m) [ZL, {ZL=Set(Cycle(Z, card>=m))}, labeled]; 
               end: ZLL:=a(1):seq(count(ZLL, size=n)*n^2, n=0..21); - Zerinvary 
               Lajos (zerinvarylajos(AT)yahoo.com), Jun 11 2008
%p A002775 a:=n->add(0+add(n!, j=1..n),j=1..n):seq(a(n), n=0..21); [From Zerinvary 
               Lajos (zerinvarylajos(AT)yahoo.com), Aug 27 2008]
%Y A002775 Cf. A047922.
%Y A002775 Contribution from Johannes W. Meijer (meijgia(AT)hotmail.com), Oct 16 
               2009: (Start)
%Y A002775 Cf. A163931 (E(x,m,n)), A001563 (n*n!), A091363 (n^3*n!), A091364 (n^4*n!).
%Y A002775 (End)
%Y A002775 Sequence in context: A081899 A057970 A154235 this_sequence A079754 A142703 
               A138403
%Y A002775 Adjacent sequences: A002772 A002773 A002774 this_sequence A002776 A002777 
               A002778
%K A002775 nonn
%O A002775 0,3
%A A002775 N. J. A. Sloane (njas(AT)research.att.com).

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