A216640 - OEIS

A216640

Number of nondecreasing arrays of n 1..n integers with the sum of their 2nd powers equal to sum(i^2,i=1..n)

%I #7 Sep 11 2012 19:31:57

%S 1,1,1,1,1,3,8,25,83,257,788,2491,7885,25099,80481,264505,884517,

%T 2994535,10208806,35095825,121699761,424273761,1487693075,5244197347,

%U 18584820912,66169376686,236592018517,849466213882,3061492852986,11072927827447

%N Number of nondecreasing arrays of n 1..n integers with the sum of their 2nd powers equal to sum(i^2,i=1..n)

%C Column 2 of A216645

%H R. H. Hardin, <a href="/A216640/b216640.txt">Table of n, a(n) for n = 1..49</a>

%e All solutions for n=6

%e ..1....3....1

%e ..2....3....1

%e ..3....4....1

%e ..4....4....4

%e ..5....4....6

%e ..6....5....6

%K nonn

%O 1,6

%A _R. H. Hardin_ Sep 11 2012