

A005528


Stormer numbers or arccotangent irreducible numbers (largest prime factor of n^2 + 1 is >= 2n.
(Formerly M0950)


8



1, 2, 4, 5, 6, 9, 10, 11, 12, 14, 15, 16, 19, 20, 22, 23, 24, 25, 26, 27, 28, 29, 33, 34, 35, 36, 37, 39, 40, 42, 44, 45, 48, 49, 51, 52, 53, 54, 56, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 69, 71, 74, 77, 78, 79, 80, 81, 82, 84, 85, 86, 87, 88, 89, 90, 92, 94, 95, 96
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OFFSET

1,2


REFERENCES

John H. Conway and R. K. Guy, The Book of Numbers, Copernicus Press, p. 246.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
J. Todd, A problem on arc tangent relations, Amer. Math. Monthly, 56 (1949), 517528.
J. Todd, Table of Arctangents. National Bureau of Standards, Washington, DC, 1951, p. 2.


LINKS

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


MATHEMATICA

Select[Range[96], FactorInteger[#^2 + 1][[1, 1]] >= 2 # &] (* JeanFrançois Alcover, Apr 11 2011 *)


CROSSREFS

Cf. A002312.
Sequence in context: A153242 A143070 A206926 * A211030 A050015 A153218
Adjacent sequences: A005525 A005526 A005527 * A005529 A005530 A005531


KEYWORD

nonn,nice,easy


AUTHOR

N. J. A. Sloane and J. H. Conway


STATUS

approved



