OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..196
EXAMPLE
a(19) = 5 because the 19th odd prime is 71 and 71 is the 5th largest distinct prime factor of 2^(71-1)-1 = 1180591620717411303423 = 3 * 11 * 31 * 43 * 71 * 127 * 281 * 86171 * 122921.
MATHEMATICA
Array[FirstPosition[FactorInteger[2^(# - 1) - 1], #][[1]] &[Prime[# + 1]] &, 50] (* Michael De Vlieger, Nov 27 2022 *)
PROG
(PARI) a(n) = my(p=prime(n+1), v=factor(2^(p-1)-1)[, 1]); vecsearch(v, p); \\ Michel Marcus, Nov 28 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
G. L. Honaker, Jr., Nov 20 2022
EXTENSIONS
More terms from Amiram Eldar, Nov 23 2022
STATUS
approved