|
| |
|
|
A125254
|
|
Smallest prime divisor of 4n-1 that is of the form 4k-1.
|
|
2
| |
|
|
3, 7, 11, 3, 19, 23, 3, 31, 7, 3, 43, 47, 3, 11, 59, 3, 67, 71, 3, 79, 83, 3, 7, 19, 3, 103, 107, 3, 23, 7, 3, 127, 131, 3, 139, 11, 3, 151, 31, 3, 163, 167, 3, 7, 179, 3, 11, 191, 3, 199, 7, 3, 211, 43, 3, 223, 227, 3, 47, 239, 3, 19, 251, 3, 7, 263, 3, 271, 11, 3, 283, 7, 3, 59, 23
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| 4n-1 always has a prime divisor congruent to 3 modulo 4.
|
|
|
REFERENCES
| T. M. Apostol, Introduction to Analytic Number Theory, Springer-Verlag, 1976, page 147.
|
|
|
LINKS
| N. Hobson, Table of n, a(n) for n = 1..1000
N. Hobson, Home page (listed in lieu of email address)
|
|
|
EXAMPLE
| The divisors of 4*9-1=35 are 5 and 7, so a(9) = 7.
|
|
|
PROG
| (PARI) vector(76, n, f=factor(4*n-1); r=0; until(f[r, 1]%4==3, r++); f[r, 1])
|
|
|
CROSSREFS
| Cf. A057205, A111863, A125255.
Sequence in context: A042373 A042775 A125255 * A093931 A153788 A167486
Adjacent sequences: A125251 A125252 A125253 * A125255 A125256 A125257
|
|
|
KEYWORD
| easy,nonn
|
|
|
AUTHOR
| Nick Hobson Nov 26 2006
|
| |
|
|
