OFFSET
1,1
COMMENTS
This is the union of the squares > 4 and A306102: numbers that are the difference of two positive squares in at least two ways (where c=0 is excluded). - M. F. Hasler, Jul 12 2018
FORMULA
EXAMPLE
9 is in the sequence since 9 = 3^2 - 0^2 = 5^2 - 4^2;
45 is in the sequence since 45 = 7^2 - 2^2 = 9^3 - 6^2 = 23^2 - 22^2.
MATHEMATICA
Select[Range@143, Length@ FindInstance[x^2 - y^2 == # && x>y>= 0, {x, y}, Integers, 2] == 2 &] (* Giovanni Resta, Jul 10 2018 *)
PROG
(PARI) select( is(n)=fordiv(n, d, d^2 > n && return; (n-d^2)%(2*d) || c++<2 || return(1)), [1..200]) \\ M. F. Hasler, Jul 10 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Henry Bottomley, Jan 13 2001
EXTENSIONS
Name edited by M. F. Hasler, Jul 10 2018
STATUS
approved