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A015915 Numbers k such that sigma(k) + 8 = sigma(k+8). 8
3, 5, 11, 23, 27, 29, 53, 59, 71, 89, 101, 131, 149, 173, 191, 233, 263, 269, 359, 389, 401, 431, 449, 479, 491, 563, 569, 593, 599, 653, 683, 701, 719, 743, 761, 821, 911, 929, 983, 1013, 1031, 1061, 1109, 1163, 1193, 1223, 1229, 1283, 1289 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Different from A023202. Below 1000000 four composites were found [27, 1615, 1885, 218984] satisfying the "sigma(k) + 8 = sigma(k+8)" relation, together with more than 8000 primes. - Labos Elemer, May 23 2000
LINKS
EXAMPLE
sigma(27) + 8 = 48 = sigma(27+8), so 27 is in the sequence.
MATHEMATICA
Select[Range[1300], DivisorSigma[1, #]+8==DivisorSigma[1, #+8]&] (* Harvey P. Dale, Jul 16 2011 *)
PROG
(PARI) is(n)=sigma(n)+8==sigma(n+8) \\ Charles R Greathouse IV, Mar 11 2014
CROSSREFS
Composite solutions are in A059118.
Sequence in context: A227806 A262431 A262085 * A275785 A106901 A154550
KEYWORD
nonn
AUTHOR
STATUS
approved

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Last modified May 18 15:56 EDT 2024. Contains 372664 sequences. (Running on oeis4.)