A219176 Smallest k > 1 such that k + n divides k^2 + n.

4, 3, 6, 5, 8, 7, 4, 6, 12, 11, 14, 13, 7, 5, 18, 17, 20, 19, 8, 12, 24, 23, 6, 25, 13, 9, 30, 29, 32, 31, 12, 18, 36, 7, 38, 37, 19, 13, 42, 41, 44, 43, 11, 24, 48, 47, 8, 21, 25, 17, 54, 53, 12, 15, 20, 30, 60, 59, 62, 61, 31, 9, 16, 13, 68, 67, 24, 36

Offset

2,1

Comments

a(n) = n if n is an odd prime.

Links

Michel Lagneau, Table of n, a(n) for n = 2..10000

Formula

a(n) exists for each n > 1; in particular, a(n) <= n + 2. - Charles R Greathouse IV, Nov 13 2012

Example

a(6) = 8 because  (8+6) = 14 divides 8^2 +  6 = 70 = 2*5*7.

Prog

(PARI) a(n)=for(k=2, n+2, if((k^2+n)%(k+n)==0, return(k))) \\ Charles R Greathouse IV, Nov 13 2012

Crossrefs

Sequence in context: A367269 A131603 A242554 * A251739 A224715 A062302

Adjacent sequences: A219173 A219174 A219175 * A219177 A219178 A219179

Keyword

nonn

Author

Michel Lagneau, Nov 13 2012

Status

approved