OFFSET
0,3
COMMENTS
For any i,j >=0 a(i)*a(j) is a member of this sequence, since (a^2 + b^2)*(c^2 + d^2) = (a*c + b*d)^2 + (a*d - b*c)^2. - Boris Putievskiy, May 05 2013
A227481(n) = number of squares in row n. - Reinhard Zumkeller, Oct 11 2013
LINKS
Reinhard Zumkeller, Rows n = 0..120 of triangle, flattened
FORMULA
T(n+1,k+1) = T(n,k) + 2*(n+k+1), k=0..n; T(n+1,0) = T(n,0) + 2*n + 1. - Reinhard Zumkeller, Oct 11 2013
EXAMPLE
Triangle T(n,k) begins:
0;
1, 2;
4, 5, 8;
9, 10, 13, 18;
16, 17, 20, 25, 32;
25, 26, 29, 34, 41, 50;
36, 37, 40, 45, 52, 61, 72;
49, 50, 53, 58, 65, 74, 85, 98;
64, 65, 68, 73, 80, 89, 100, 113, 128;
81, 82, 85, 90, 97, 106, 117, 130, 145, 162;
100, 101, 104, 109, 116, 125, 136, 149, 164, 181, 200;
...
PROG
(Haskell)
a069011 n k = a069011_tabl !! n !! k
a069011_row n = a069011_tabl !! n
a069011_tabl = map snd $ iterate f (1, [0]) where
f (i, xs@(x:_)) = (i + 2, (x + i) : zipWith (+) xs [i + 1, i + 3 ..])
-- Reinhard Zumkeller, Oct 11 2013
CROSSREFS
KEYWORD
AUTHOR
Henry Bottomley, Apr 02 2002
STATUS
approved