id:A106544 - OEIS Search Results

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Perfect squares n^2 which are not the sum of two primes (otherwise 0).

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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; listen)

	OFFSET	`1,11`
	COMMENT	`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)`
	FORMULA	`a(n) = n^2 - A106545(n).`
	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.`
	CROSSREFS	`Cf. A106545-A106548, A106562-A106564, A106571, A106573-A106575, A106577.` `Sequence in context: A045509 A033187 A106547 this_sequence A079842 A014756 A014748` `Adjacent sequences: A106541 A106542 A106543 this_sequence A106545 A106546 A106547`
	KEYWORD	`easy,nonn`
	AUTHOR	`Alexandre Wajnberg (alexandre.wajnberg(AT)ulb.ac.be), May 08 2005`
	EXTENSIONS	`Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), May 12 2005`

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Last modified December 21 10:15 EST 2009. Contains 171081 sequences.

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