OFFSET
1,2
COMMENTS
Except for 1 and 361=19^2 terms listed are primes.
Most a(n) are primes p such that 2p+1 is composite A053176. Nonprime a(n) (except a(1) = 1) are the powers or the products of primes from a(n). For example, 361 = 19^2, 589 = 19*31, 961 = 31^2, 1333 = 31*43, 1849 = 43^2, 2071 = 19*109, 2077 = 31*67, 2201 = 31*71, 2449 = 31*79, 2537 = 43*59, 2641 = 19*139, 2881 = 43*67, 2983 = 19*157, 3053 = 43*71, 3173 = 19*167, ..., 6859 = 19^3. - Alexander Adamchuk, Jul 28 2006
LINKS
Enrique PĂ©rez Herrero, Table of n, a(n) for n=1..50000
MATHEMATICA
Do[s=1+Divisors[n]; s1=Flatten[Position[PrimeQ[s], True]]; s2=Part[s, s1]; If[Equal[s2, {2, 3, 7}], Print[n/6]], {n, 1, 10000}] (* Alexander Adamchuk, Jul 28 2006 *)
Select[Range[600], Denominator[BernoulliB[6#]]==42&] (* Harvey P. Dale, Jan 09 2024 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Mar 24 2002
EXTENSIONS
Corrected and extended by Ralf Stephan, Oct 21 2002
More terms from Alexander Adamchuk, Jul 28 2006
STATUS
approved