OFFSET
1,1
COMMENTS
Also, the number of ways to write n as p^2-q^2-r^2-s^2 with 0 <= min(q, r, s) and max(q, r, s) < n and max(q+r, r+s, s+q) <= n.
LINKS
Rémy Sigrist, Table of n, a(n) for n = 1..1000
Rémy Sigrist, Illustration of the first terms
Rémy Sigrist, C program for A284385
Eric Weisstein's World of Mathematics, Polyiamond
Wikipedia, Polyiamond
Indranil Ghosh, Python Program to compute the first 1000 terms (translated from the C program by Rémy Sigrist)
EXAMPLE
See Links section.
CROSSREFS
KEYWORD
nonn
AUTHOR
Rémy Sigrist, Mar 26 2017
STATUS
approved