OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A130199(n)/2. Multiplying by 2 doesn't change evilness. Hence evil oblong numbers are twice evil triangular numbers.
EXAMPLE
3 belongs to the sequence because the binary expansion of 3 is 11 - contains an even number of ones.
MATHEMATICA
Select[Table[n(n + 1)/2, {n, 0, 100}], EvenQ[Plus @@ IntegerDigits[ #, 2]] &]
CROSSREFS
KEYWORD
nonn
AUTHOR
Tanya Khovanova, May 16 2007
EXTENSIONS
a(1) = 0 inserted by Amiram Eldar, Dec 09 2019
STATUS
approved