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A178431
Joint-rank array of the sums of two primes.
2
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
1,2
COMMENTS
Joint-rank arrays are defined at A157927 for arrays in which duplicates occur (and otherwise, at A182801).
EXAMPLE
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.
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Clark Kimberling, Dec 21 2010
STATUS
approved