|
| |
|
|
A256503
|
|
Smallest k>=1 such that n^2 + (n+1)^2 + ... + (n+k)^2 is prime or a(n)=0 if there is no such k.
|
|
4
|
|
|
|
1, 1, 5, 1, 1, 2, 1, 0, 1, 0, 0, 1, 5, 1, 0, 0, 1, 5, 1, 0, 5, 1, 5, 1, 1, 0, 0, 0, 1, 1, 0, 1, 0, 1, 1, 0, 0, 5, 1, 0, 0, 1, 0, 0, 0, 0, 1, 5, 0, 1, 5, 2, 0, 0, 0, 2, 0, 0, 0, 1, 0, 2, 5, 0, 1, 2, 0, 0, 1, 1, 0, 1, 0, 0, 0, 2, 0, 0, 1, 0, 5, 1, 0, 1, 1, 2, 1
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,3
|
|
|
COMMENTS
|
Every term is either 0 or 1 or 2 or 5.
a(n)=0 if and only if n is in A256385.
|
|
|
LINKS
|
Table of n, a(n) for n=1..87.
|
|
|
FORMULA
|
1) if 2n^2+2n+1 is prime, then a(n)=1;
2) if 2n^2+2n+1 is not prime, but 3n^2+6n+5 is prime, then a(n)=2;
3) if 2n^2+2n+1 and 3n^2+6n+5 are both composite numbers, but 6n^2+30n+55 is prime, then a(n)=5;
4) otherwise, a(n)=0.
|
|
|
CROSSREFS
|
Cf. A000290, A256385, A089306.
Sequence in context: A130511 A320410 A011396 * A036791 A180136 A010129
Adjacent sequences: A256500 A256501 A256502 * A256504 A256505 A256506
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
Vladimir Shevelev, Mar 31 2015
|
|
|
EXTENSIONS
|
More terms from Peter J. C. Moses, Mar 31 2015
|
|
|
STATUS
|
approved
|
| |
|
|
