OFFSET
1,1
COMMENTS
Subsequence of A144291 - R. J. Mathar, Jan 17 2009
Prime factors counted with multiplicity. - Harvey P. Dale, Aug 23 2020
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
EXAMPLE
If n=8=2*2*2(number of prime factors = 3) and n+1=9=3*3(number of prime factors = 2), then 8*9/2=36=a(1). If n=20=2*2*5(number of prime factors = 3) and n+1=21=3*7(number of prime factors = 2), then 20*21/2=210=a(2). If n=24=2*2*2*3(number of prime factors = 4) and n+1=25=5*5(number of prime factors = 2), then 24*25/2=300=a(3), etc.
MATHEMATICA
(Times@@#)/2&/@Select[Partition[Range[250], 2, 1], AllTrue[ #, CompositeQ] && PrimeOmega[#[[1]]]>PrimeOmega[#[[2]]]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Aug 23 2020 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Juri-Stepan Gerasimov, Dec 15 2008
EXTENSIONS
Corrected definition. 2926 inserted and extended. - R. J. Mathar, Jan 17 2009
STATUS
approved