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A116565
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Hexagonal numbers for which the number of divisors is also a hexagonal number.
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0
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1, 28, 45, 153, 325, 4753, 7381, 29161, 56953, 65341, 73536, 166753, 266085, 270480, 354061, 1062153, 1383616, 3123750, 3525840, 3873936, 5247180, 5649841, 6060421, 6644835, 6835753, 6924781, 7006896, 7870528, 9925740, 10285380, 12708361
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,2
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COMMENTS
| The hexagonal numbers are numbers of the form n(2n-1) (A000384).
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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.
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MAPLE
| with(numtheory): a:=proc(n) local h: h:=tau(n*(2*n-1)): if type(sqrt(1+8*h)/4+1/4, integer)=true then n*(2*n-1) else fi end: seq(a(n), n=0..3000); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 06 2006
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CROSSREFS
| Cf. A000384.
Sequence in context: A144581 A075875 A116541 * A039615 A046419 A063770
Adjacent sequences: A116562 A116563 A116564 * A116566 A116567 A116568
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KEYWORD
| nonn
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AUTHOR
| Luc Stevens (lms022(AT)yahoo.com), Apr 03 2006
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EXTENSIONS
| More terms from Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 06 2006
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