OFFSET
1,2
LINKS
Clark Kimberling, Table of n, a(n) for n = 1..1000
EXAMPLE
A001751 = ordered sequence of primes and twice-primes: 2,3,4,5,6,7,10,... in which the primes occupy ranks 1,2,4,6,...
MATHEMATICA
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Feb 13 2018
STATUS
approved