login
This site is supported by donations to The OEIS Foundation.

 

Logo

Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS".
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A106544 Perfect squares n^2 which are not the sum of two primes (otherwise 0). 12
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; text; internal format)
OFFSET

1,11

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)

LINKS

Table of n, a(n) for n=1..81.

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 * A079842 A014756 A014748

Adjacent sequences:  A106541 A106542 A106543 * A106545 A106546 A106547

KEYWORD

easy,nonn

AUTHOR

Alexandre Wajnberg, May 08 2005

EXTENSIONS

Extended by Ray Chandler, May 12 2005

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified November 18 05:25 EST 2017. Contains 294853 sequences.