

A054903


Composite numbers n such that sigma(n)+6 = sigma(n+6), where sigma=A000203.


4



104, 147, 596, 1415, 4850, 5337, 370047, 1630622, 35020303, 120221396, 3954451796, 742514284703
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OFFSET

1,1


COMMENTS

Complement of A023201 with respect to A015914.
Intersection of A015914 and A018252.
Below 1000000 there are only 7 such composite numbers, compared with more than 16000 primes.
a(13) > 10^13.  Giovanni Resta, Jul 11 2013


REFERENCES

J.M. De Koninck, Ces nombres qui nous fascinent, Entry 104, p. 37, Ellipses, Paris 2008.


LINKS

Table of n, a(n) for n=1..12.


EXAMPLE

n=104,Sigma[104]+6=210+6=216=Sigma[104+6]=Sigma[110]
a(4) = 1415 = 5*283, 1415+6 = 1421 = 7*7*29:
sigma(1415) = 1+5+283+1415 = 1704,
sigma(1421) = 1+7+29+49+203+1421 = 1710 = sigma(1415)+6.


PROG

(PARI) forcomposite(n=9, 1e7, if(sigma(n)+6==sigma(n+6), print1(n", "))) \\ Charles R Greathouse IV, Feb 14 2013


CROSSREFS

Cf. A015913A015917, A023200A023203, A046133, A001359, A054799.
Sequence in context: A095641 A055036 A052476 * A074228 A168528 A234261
Adjacent sequences: A054900 A054901 A054902 * A054904 A054905 A054906


KEYWORD

nonn,more


AUTHOR

Labos Elemer, May 23 2000


EXTENSIONS

More terms from Jud McCranie, May 25 2000
New definition from Reinhard Zumkeller, Jan 27 2009
Edited by N. J. A. Sloane, Jan 31 2009 at the suggestion of R. J. Mathar.
a(12) from Giovanni Resta, Jul 11 2013


STATUS

approved



