A few more(?): Somos sequences are integers. And 1,1,-1,x,...,(s[n-1]*s[n-3]+s[n-2]^2)/s[n-4] gives polynomials. Which factor only if n does. # partitions of n into ordered 4tuples of triangular numbers = sum of divisors of 2n+1. # partitions into parts differing by at least 2 = # partitions into parts +-1 mod 5. (Rogers-Ramanujan). The tetrahedral analogy of Koch's Snowflake construction makes a cube. --rwg