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 A178431 #5 Mar 30 2012 18:57:11 %S A178431 1,2,2,4,3,4,6,5,5,6,9,7,7,7,9,11,10,8,8,10,11,14,12,12,10,12,12,14, %T A178431 16,15,13,13,13,13,15,16,19,17,17,15,17,15,17,17,19,23,20,18,18,18,18, %U A178431 18,18,20,23,25,24,21,20,21,20,21,20,21,24,25 %N A178431 Joint-rank array of the sums of two primes. %C A178431 Joint-rank arrays are defined at A157927 for arrays in which duplicates occur (and otherwise, at A182801). %e A178431 A corner of the array A178400 of sums of two primes: %e A178431 4...5...7...9..13... %e A178431 5...6...8..10..14... %e A178431 7...8..10..12..14... %e A178431 9..10..12..14..18... %e A178431 Each of these P(i,j) is replaced by its rank when all the %e A178431 numbers P(h,k) are jointly ranked, leaving A178431: %e A178431 1...2...4...6...9... %e A178431 2...3...5...7..10... %e A178431 4...5...7...8..12... %e A178431 6...7...8..10..13... %e A178431 The number of distinct sums p+q <=13 is 9. %Y A178431 Cf. A014092, A157927, A178400. %K A178431 nonn,tabl %O A178431 1,2 %A A178431 _Clark Kimberling_, Dec 21 2010