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A243941
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Number of decompositions of 36*n^2 into the sum of two twin prime pairs.
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3
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1, 2, 2, 5, 5, 3, 6, 3, 6, 8, 5, 6, 7, 6, 10, 10, 9, 8, 15, 10, 13, 8, 23, 5, 16, 21, 10, 20, 13, 30, 12, 14, 26, 16, 35, 16, 21, 22, 23, 38, 17, 28, 20, 36, 37, 16, 30, 27, 35, 33, 35, 29, 25, 34, 43, 51, 32, 44, 28, 39, 51, 40, 49, 31, 76, 31, 30, 52, 36, 103
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OFFSET
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1,2
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COMMENTS
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Following a remark of M. T. Kong Tong on seqfan, there seems to be always at least one way to partition (6n)^2 into the sum of two prime pairs. This sequence gives the number of different solutions.
If there are only finitely many prime twins, this sequence will contain an infinite number of zeros.
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REFERENCES
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Liang Ding Xiang, Problem 93#, Bulletin of Mathematics (Wuhan), 6 (1992), 41. ISSN 0488-7395.
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LINKS
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EXAMPLE
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A solution is denoted by {p,q} where p,p+2,q,q+2 are all primes and p<=q.
a(10) = 8 because there are 8 ways to partition 3600 in this way.
The solution using the smallest prime numbers is 11+13+1787+1789 = 3600.
All 8 solutions are {11, 1787}, {101, 1697}, {179, 1619}, {191, 1607}, {311, 1487}, {347,1451}, {521, 1277} and {569, 1229}.
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PROG
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(PARI) a(n)={my(m=18*n^2, s=0); forprime(p=5, m/2, if(isprime(m-p) && isprime(p-2) && isprime(m-p+2), s++)); s} \\ Andrew Howroyd, Sep 17 2019
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CROSSREFS
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Cf. A243940 (decompositions of n^2 into 4 primes).
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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