cp's OEIS Frontend

A284385 Number of fixed convex n-iamonds (or polyiamonds with n cells).

%I A284385 #18 Feb 16 2025 08:33:43
%S A284385 2,3,6,8,6,7,12,15,8,9,18,18,8,15,24,23,12,12,24,30,12,17,36,31,14,21,
%T A284385 30,30,18,24,42,42,14,21,48,38,14,33,48,45,24,18,42,54,24,35,66,48,20,
%U A284385 36,48,44,24,40,72,63,18,27,72,60,26,51,66,62,36,30,60
%N A284385 Number of fixed convex n-iamonds (or polyiamonds with n cells).
%C A284385 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.
%H A284385 Rémy Sigrist, <a href="/A284385/b284385.txt">Table of n, a(n) for n = 1..1000</a>
%H A284385 Rémy Sigrist, <a href="/A284385/a284385.png">Illustration of the first terms</a>
%H A284385 Rémy Sigrist, <a href="/A284385/a284385.txt">C program for A284385</a>
%H A284385 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/Polyiamond.html">Polyiamond</a>
%H A284385 Wikipedia, <a href="https://en.wikipedia.org/wiki/Polyiamond">Polyiamond</a>
%H A284385 Indranil Ghosh, <a href="/A284385/a284385_1.txt">Python Program to compute the first 1000 terms</a> (translated from the C program by _Rémy Sigrist_)
%e A284385 See Links section.
%Y A284385 Cf. A000577, A001420, A096004.
%K A284385 nonn
%O A284385 1,1
%A A284385 _Rémy Sigrist_, Mar 26 2017