OFFSET
1,1
COMMENTS
From Robert Israel, Jan 18 2023: (Start)
a(n) = 5 if n == 1 (mod 5).
a(n) = 6*n - 1 if n is in A024898. (End)
REFERENCES
G. Pólya and G. Szegő, Problems and Theorems in Analysis I (Springer 1924, reprinted 1972), Part Eight, Chap. 2, Section 2, Problem 96.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
For n = 13, 6*n - 1 = 77 = 7*11; 7 == 1 (mod 6), but 11 == 5 (mod 6), so a(13) = 11.
MAPLE
f:= n -> min(select(p -> p mod 6 = 5, numtheory:-factorset(6*n-1))):
map(f, [$1..100]); # Robert Israel, Jan 18 2023
PROG
(PARI) for(k=1, 60, my(f=factor(6*k-1)[, 1]); for(j=1, #f, if(f[j]%6==5, print1(f[j], ", "); break))) \\ Hugo Pfoertner, Dec 25 2019
CROSSREFS
KEYWORD
nonn,look
AUTHOR
Reinhard Zumkeller, Aug 20 2005
STATUS
approved