OFFSET
1,1
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
a(1)=4 because 2*4-1=7=prime; a(2)=6 because 2*6-1=11=prime.
MATHEMATICA
Select[(#+1)/2&/@Prime[Range[2, 100]], CompositeQ] (* Harvey P. Dale, May 21 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Mar 10 2010
EXTENSIONS
Entries checked by R. J. Mathar, Apr 26 2010
STATUS
approved