OFFSET
1,1
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
Kevin A. Broughan and Zhou Qizhi, Flat primes and thin primes, Bulletin of the Australian Mathematical Society, Vol. 82, No. 2 (2010), pp. 282-292, alternative link.
FORMULA
a(n) ~ Pi^2/4 * n.
MATHEMATICA
Select[Range[3, 150, 2], SquareFreeQ[(# - 1)/2^IntegerExponent[# - 1, 2]] &] (* Amiram Eldar, Aug 30 2020 *)
PROG
(PARI) is(n)=n%2&&issquarefree((n-1)>>valuation(n-1, 2)) \\ corrected by Amiram Eldar, Aug 30 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Charles R Greathouse IV, Jul 11 2011
EXTENSIONS
Data corrected by Amiram Eldar, Aug 30 2020
STATUS
approved