A108321 a(n) = n^2 if n^2 is not the difference of two primes; otherwise a(n) = 0.

0, 0, 0, 0, 25, 0, 49, 0, 0, 0, 121, 0, 169, 0, 0, 0, 289, 0, 361, 0, 0, 0, 529, 0, 625, 0, 729, 0, 841, 0, 961, 0, 0, 0, 1225, 0, 1369, 0, 0, 0, 1681, 0, 1849

Offset

0,5

Comments

This sequence is also n^2 - A106546

Links

Table of n, a(n) for n=0..42.

Example

a(4)=0 because the fourth perfect square 16 is the difference between two primes: 19-3. a(5)=25 figures here because the nearest prime greater than 25 is 29 and the difference 29-25 is 4 (an even number >2), thus not a prime; all other greater primes are odd and the difference with 25 will give an even number, thus again not a prime.

Crossrefs

Cf. A106546, A106564, A098108, A106571.

Sequence in context: A005079 A167624 A181614 * A059062 A179809 A110416

Adjacent sequences: A108318 A108319 A108320 * A108322 A108323 A108324

Keyword

easy,nonn

Author

Alexandre Wajnberg, Jun 30 2005

Status

approved