OFFSET
1,2
COMMENTS
a(n) is the smallest k >= 0 such that A231015(k) = n.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 1..145
EXAMPLE
a(1) = 1: 1^2 = 1.
a(2) = 3: -1^2 + 2^2 = 3.
a(7) = 0: 1^2 + 2^2 - 3^2 + 4^2 - 5^2 - 6^2 + 7^2 = 0.
MAPLE
b:= proc(n, i) option remember; (m-> n<=m and (n=m or
b(abs(n-i^2), i-1) or b(n+i^2, i-1)))(i*(i+1)*(2*i+1)/6)
end:
g:= proc(n) option remember; local k; for k while not b(n, k) do od; k end:
a:= proc(n) option remember; local k; for k from 0 while not g(k)=n do od; k end:
seq(a(n), n=1..47);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Dec 30 2025
STATUS
approved
