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A106544
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Perfect squares n^2 which are not the sum of two primes (otherwise 0).
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12
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1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 121, 0, 0, 0, 0, 0, 289, 0, 0, 0, 0, 0, 529, 0, 625, 0, 0, 0, 0, 0, 961, 0, 0, 0, 0, 0, 0, 0, 1521, 0, 1681, 0, 0, 0, 2025, 0, 0, 0, 0, 0, 2601, 0, 2809, 0, 0, 0, 3249, 0, 3481, 0, 0, 0, 0, 0, 4225, 0, 4489, 0, 0, 0, 0, 0, 5329, 0, 0, 0, 0, 0, 6241, 0, 6561
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,11
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COMMENTS
| For odd n, n^2 is odd so the two primes must be opposite in parity. Lesser prime must be 2 and greater prime must be n^2-2. Thus for odd n, n^2 is the sum of two primes iff n^2-2 is prime. (Chandler)
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FORMULA
| a(n) = n^2 - A106545(n).
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EXAMPLE
| a(10)=0 because 10^2=100=97+3 (sum of two primes)
a(11)=11^2=121, which is impossible to obtain summing two primes.
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CROSSREFS
| Cf. A106545-A106548, A106562-A106564, A106571, A106573-A106575, A106577.
Sequence in context: A045509 A033187 A106547 * A079842 A014756 A014748
Adjacent sequences: A106541 A106542 A106543 * A106545 A106546 A106547
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KEYWORD
| easy,nonn
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AUTHOR
| Alexandre Wajnberg (alexandre.wajnberg(AT)ulb.ac.be), May 08 2005
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EXTENSIONS
| Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), May 12 2005
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