A178431 Joint-rank array of the sums of two primes.
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, 16, 15, 13, 13, 13, 13, 15, 16, 19, 17, 17, 15, 17, 15, 17, 17, 19, 23, 20, 18, 18, 18, 18, 18, 18, 20, 23, 25, 24, 21, 20, 21, 20, 21, 20, 21, 24, 25
Offset: 1
Examples
A corner of the array A178400 of sums of two primes: 4...5...7...9..13... 5...6...8..10..14... 7...8..10..12..14... 9..10..12..14..18... Each of these P(i,j) is replaced by its rank when all the numbers P(h,k) are jointly ranked, leaving A178431: 1...2...4...6...9... 2...3...5...7..10... 4...5...7...8..12... 6...7...8..10..13... The number of distinct sums p+q <=13 is 9.
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