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A003624 Duffinian numbers: n composite and relatively prime to sigma (n).
(Formerly M3324)
+0
2
4, 8, 9, 16, 21, 25, 27, 32, 35, 36, 39, 49, 50, 55, 57, 63, 64, 65, 75, 77, 81, 85, 93, 98, 100, 111, 115, 119, 121, 125, 128, 129, 133, 143, 144, 155, 161, 169, 171, 175, 183, 185, 187, 189, 201, 203, 205, 209, 215, 217, 219, 221, 225, 235, 237, 242, 243, 245, 247 (list; graph; listen)
OFFSET

1,1

REFERENCES

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

"The Duffinian Numbers" by L. Richard Duffy, J. Rec. Math., 12 (1979), 112-115.

J. Roberts, Lure of the Integers, Math. Assoc. America, 1992, p. 64.

LINKS

T. D. Noe, Table of n, a(n) for n=1..1000

CROSSREFS

Cf. A014567

Sequence in context: A134344 A119315 A010390 this_sequence A100657 A140104 A127398

Adjacent sequences: A003621 A003622 A003623 this_sequence A003625 A003626 A003627

KEYWORD

nonn

AUTHOR

N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein

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Last modified December 20 16:54 EST 2009. Contains 171081 sequences.


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