This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A087084 #1 Sep 13 2003 03:00:00 %S A087084 0,0,2,32,1536,1048576,171798691840,1770887431076116955136, %T A087084 76223250190290215815795912064716079366144 %N A087084 Number of integer elements in the subsets of the subsets of the integers 1 to n. %D A087084 Alan Sutcliffe, Divisors and Common Factors in Sets of Integers, awaiting publication. %F A087084 (n-1)*2^(n-3+2^(n-1)) %e A087084 a(3)=32 since the 16 subsets of the sets ( ) (1) (2) (1,2) are ( ) (( )) ((1)) ((2)) ((1,2)) (( ) (1)) (( ) (2)) (( ) (1,2)) ((1) (2)) ((1) (1,2)) ((2) (1,2)) (( ) (1) (2)) (( ) (1) (1,2)) (( ) (2) (1,2)) ((1) (2) (1,2)) (( ) (1) (2) (1,2)) and these contain 32 integer elements. %Y A087084 A001146 gives the number of subsets of the subsets of the integers 1 to n. A028369 gives the number of subset elements in the subsets of the subsets of the integers 1 to n. %K A087084 easy,nonn %O A087084 0,3 %A A087084 Alan Sutcliffe (alansut(AT)ntlworld.com), Aug 13 2003