OFFSET
3,1
COMMENTS
a(4)=0 is conjectured.
a(6)=0 because all hexagonal numbers are triangular numbers (see A176948).
LINKS
Michel Marcus, Table of n, a(n) for n = 3..70
Michel Marcus, Triples for n = 3..70
EXAMPLE
PROG
(PARI) p(s, n) = ((s-2)*n^2 - (s-4)*n)/2;
lista(nn, n) = {my(v = vector(nn, k, p(n, k))); v = select(x->(tp(x)==n), v); my(kh = oo, kv = oo); for (i=1, #v, for (j=1, i, my(h2 = v[i]^2 + v[j]^2, h); if (issquare(h2, &h), if (h < kh, kh = h; kv = [v[j], v[i], kh]); ); ); ); kh; }
a(n) = {if (n==4, return (0)); if (n==6, return (0)); my(nn = 2); while ((res=lista(nn, n)) == oo, nn *= 2); res; }
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Marcus, May 06 2021
STATUS
approved