OFFSET
2,1
COMMENTS
p=prime(n) is in A001220 if and only if a(n) is equal to A014664(n). So far this is known to hold only for p=1093 and p=3511.
This happens for n=183 and 490, that is for p=prime(183)=1093 and p=prime(490)=3511, with values 364 and 1755 (see b-files). - Michel Marcus, Jun 29 2014
If 2^q-1 is p=prime(n), i.e., for n in A016027, then a(n)=pq and lpf(2^a(n)-1)=p. - Thomas Ordowski, Feb 04 2019
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 2..10000
FORMULA
a(n) = prime(n)*A014664(n) for all odd primes that are not Wieferich. - Thomas Ordowski, Feb 04 2019
MAPLE
seq(numtheory:-order(2, ithprime(i)^2), i=2..1000); # Robert Israel, Jul 08 2014
MATHEMATICA
Table[MultiplicativeOrder[2, Prime[n]^2], {n, 2, 100}] (* Jean-François Alcover, Jul 08 2014 *)
PROG
(PARI) forprime(p=3, 10^2, print1(znorder(Mod(2, p^2)), ", "))
CROSSREFS
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Jun 14 2014
STATUS
approved