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A054903

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

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

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

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

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

URL: https://oeis.org/A054903