OFFSET
1,1
COMMENTS
This is A034953 without the 3. [From R. J. Mathar, Feb 21 2009]
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
If n=3(prime) and n=4(nonprime), then 3*4/2=6=a(1). If n=5(prime) and n=6(nonprime), then 5*6/2=15=a(2). If n=7(prime) and n=8(nonprime), then 7*8/2=28=a(3). If n=11(prime) and n=12(nonprime), then 11*12/2=66=a(4). If n=13(prime) and n=14(nonprime), then 13+14/2=91=a(5), etc.
MATHEMATICA
Table[(p(p+1))/2, {p, Prime[Range[2, 50]]}] (* Harvey P. Dale, Dec 28 2023 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Dec 15 2008
EXTENSIONS
Corrected definition. Inserted 2701, extended beyond 11175. - R. J. Mathar, Dec 19 2008
STATUS
approved