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A106575
Perfect squares which are both the sum and the difference of two primes.
13
4, 9, 16, 36, 64, 81, 100, 144, 196, 225, 256, 324, 400, 441, 484, 576, 676, 784, 900, 1024, 1089, 1156, 1296, 1444, 1600, 1764, 1936, 2116, 2304, 2500, 2704, 2916, 3136, 3364, 3600, 3844, 4096, 4356, 4624, 4900, 5184, 5476, 5776, 6084, 6400, 6724, 7056
OFFSET
1,1
COMMENTS
Equals A106548 with 0's removed.
Appears to contain all even squares.
By well-known conjectures, every even integer > 2 is both the sum and the difference of two primes; this would be a special case. - Franklin T. Adams-Watters, Sep 13 2015
EXAMPLE
2^2 = 4 is in the sequence because it is the sum of two primes (2+2) and the difference of two primes (7-3). 10^2 = 100 is in the sequence because it is the sum and the difference of two primes: 97+3 (or 89+11) and 103-3. 11^2 = 121 is not in the sequence because it is neither the sum nor the difference of two primes. 13^2 = 169 is the sum of two primes (167+2), but it doesn't figure here since it is not the difference of two primes.
PROG
(Magma) [ s: n in [1..85] | exists(t){ k: k in [1..s] | s-k gt 0 and IsPrime(k) and IsPrime(s-k) } and exists(u){ k: k in [1..s] | IsPrime(k) and IsPrime(s+k) } where s is n^2 ]; /* Klaus Brockhaus, Nov 17 2010 */
KEYWORD
easy,nonn
AUTHOR
Alexandre Wajnberg, May 09 2005
EXTENSIONS
Extended by Ray Chandler, May 12 2005
Edited by Klaus Brockhaus, Nov 17 2010
STATUS
approved