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 A217446 Sum of the squares of numbers obtained by digit permutations of the concatenation of first n numbers. 1

%I

%S 1,585,331668,213208980,156226437720,129158041750920,

%T 119164964083502400,121503028361696976960,135757575541042424323200,

%U 165013333307050666667644800,216831999996550400000012812800,306342399999513113600000180544000,463124479999926454528000002723302400

%N Sum of the squares of numbers obtained by digit permutations of the concatenation of first n numbers.

%H Alois P. Heinz, <a href="/A217446/b217446.txt">Table of n, a(n) for n = 1..100</a>

%F a(n) = (1/12)*(n+1)!*(n*R'(n)+(3*n+2)*R(n)^2) with R(n) = (10^n-1)/9 and R'(n) = (10^(2*n)-1)/99.

%e a(1) = 1^2 = 1.

%e a(2) = 12^2 + 21^2 = 585.

%e a(3) = 123^2 + 132^2 + 213^2 + 231^2 + 312^2 + 321^2 = 331668.

%p R:= n-> (10^n-1)/9: RP:= n-> (10^(2*n)-1)/99:

%p a:= n-> (1/12)*(n+1)!*(n*RP(n)+(3*n+2)*R(n)^2):

%p seq (a(n), n=1..15); # _Alois P. Heinz_, Oct 03 2012

%Y Cf. A071268.

%K nonn,base

%O 1,2

%A _Roger CuculiÃ¨re_, Oct 03 2012

%E More terms from _Alois P. Heinz_, Oct 03 2012

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Last modified May 21 00:57 EDT 2019. Contains 323429 sequences. (Running on oeis4.)