OFFSET
1,2
COMMENTS
Other definition: Square array read by antidiagonal: T(n,k), n>=0, k>=1, in which column k lists the numbers A040000 (1, 2, 2, 2, 2...) interleaved with k^(1/2)-1 zeros, if k is a square otherwise column k lists only zeros.
The sum of elements of the n-th antidiagonal equals the number of divisors of n. In other words, the antidiagonal sums give A000005.
FORMULA
sum_{k=1...n} a(n-k,k) = A000005(n) for all n>0. - M. F. Hasler, Feb 02 2013
EXAMPLE
First 16 elements of first 16 rows of the square array are
1,0,0,1,0,0,0,0,1,0,0,0,0,0,0,1,...
2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,...
2,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,...
2,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,...
2,0,0,2,0,0,0,0,0,0,0,0,0,0,0,2,...
2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,...
2,0,0,2,0,0,0,0,2,0,0,0,0,0,0,0,...
2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,...
2,0,0,2,0,0,0,0,0,0,0,0,0,0,0,2,...
2,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,...
2,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,...
2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,...
2,0,0,2,0,0,0,0,2,0,0,0,0,0,0,2,...
2,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,...
2,0,0,2,0,0,0,0,0,0,0,0,0,0,0,0,...
2,0,0,0,0,0,0,0,2,0,0,0,0,0,0,0,...
...
For n = 3 the sum of the third antidiagonal is 2+0+0 = d(3) = A000005(3) = 2.
For n = 16 the sum of the 16th antidiagonal is 2+0+0+2+0+0+0+0+0+0+0+0+0+0+0+1 = d(16) = A000005(16) = 5.
PROG
(PARI) A221645(n, m)={my(t); issquare(m, &t)||return; n||return(1); n%t & return; 2} \\ M. F. Hasler, Feb 02 2013
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Omar E. Pol, Feb 02 2013
STATUS
approved