OFFSET
1,2
COMMENTS
No more terms < 22155000. - David Wasserman, Jan 09 2009
EXAMPLE
a(3) <> 3 because we can write 3^2 = a(2)^2 + a(2)^2 + a(1)^2 by using not more than 3 terms.
But it is impossible to write 4^2 as the sum of at most three squares of the previous elements, thus a(3)=4.
PROG
(PARI) canMake(n, v, i, left) = local(c); if (i == 0, return(n <= left)); c = v[i]; if (n > left*c, return(0)); if (!(n%c), return(1)); forstep (j = n\c, 0, -1, if (canMake(n - j*c, v, i - 1, left - j), return(1))); 0;
v = vector(60); x = 2; for (m = 2, 61, while (canMake(x^2, v, m - 2, m), x++); v[m - 1] = x^2; print1(x, ", "); x++); \\ David Wasserman, Jan 09 2009
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Stefan Steinerberger, Nov 02 2005
EXTENSIONS
More terms from David Wasserman, Jan 09 2009
STATUS
approved