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A007373
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Numbers n such that sigma (n+2) = sigma (n).
(Formerly M5234)
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15
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33, 54, 284, 366, 834, 848, 918, 1240, 1504, 2910, 2913, 3304, 4148, 4187, 6110, 6902, 7169, 7912, 9359, 10250, 10540, 12565, 15085, 17272, 17814, 19004, 19688, 21410, 21461, 24881, 25019, 26609, 28124, 30592, 30788, 31484, 38210, 38982
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 840.
J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 33, pp 12, Ellipses, Paris 2008.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
A. Weingartner, On the Solutions of sigma(n) = sigma(n+k), Journal of Integer Sequences, Vol. 14 (2011), #11.5.5.
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LINKS
| Moshe Levin, Table of n, a(n) for n = 1..1000
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
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MATHEMATICA
| Flatten[Position[Partition[DivisorSigma[1, Range[300000]], 3, 1], {x_, _, x_}]] (* From Harvey P. Dale, Aug 08 2011 *)
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PROG
| (PARI) je=[]; for(n=1, 10^5, a=sigma(n); b=sigma(n+2); if(a==b, je=concat(je, n))); je
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CROSSREFS
| Essentially the same as A055574.
Cf. A002961, A015861, A015863, A015865, A015866, A015867, A015876, A015877, A015880, A015881, A015882, A015883, A181647. [From Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Nov 03 2010]
Sequence in context: A014976 A109407 A204374 * A024628 A061864 A075810
Adjacent sequences: A007370 A007371 A007372 * A007374 A007375 A007376
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KEYWORD
| nonn
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Mira Bernstein, Robert G. Wilson v (rgwv(AT)rgwv.com)
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EXTENSIONS
| More terms from Jason Earls (zevi_35711(AT)yahoo.com), Jul 20 2001
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