OFFSET
1,2
COMMENTS
The hexagonal numbers are numbers of the form n(2n-1) (A000384).
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..500
EXAMPLE
45 is in the sequence because 45=5(2*5-1) is a hexagonal number having 6 divisors (1,3,5,9,15,45) and 6=2(2*2-1) is also a hexagonal number.
MAPLE
with(numtheory): a:=proc(n) local h: h:=tau(n*(2*n-1)): if type(sqrt(1+8*h)/4+1/4, integer) then n*(2*n-1) else fi end: seq(a(n), n=0..3000); # Emeric Deutsch, Apr 06 2006
MATHEMATICA
With[{hex=PolygonalNumber[6, Range[3000]]}, Select[hex, MemberQ[hex, DivisorSigma[0, #]]&]] (* Harvey P. Dale, Mar 10 2024 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Luc Stevens (lms022(AT)yahoo.com), Apr 03 2006
EXTENSIONS
More terms from Emeric Deutsch, Apr 06 2006
STATUS
approved