1,2

Table of n, a(n) for n=1..65.

a(1)=1 because 3*prime(1)-4=2 is prime and 3*prime(1)+4=10 is composite; a(2)=4 because 3*prime(4)-4=17 is prime and 3*prime(4)+4=25 is composite.

Sequence in context: A095096 A179242 A104425 * A080746 A246362 A069909

Adjacent sequences: A174255 A174256 A174257 * A174259 A174260 A174261

nonn,easy

Juri-Stepan Gerasimov, Mar 14 2010

Corrected by Charles R Greathouse IV, Mar 19 2010

approved