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 A015913 Numbers k such that sigma(k) + 4 = sigma(k+4). 19
 3, 7, 13, 19, 37, 43, 67, 79, 97, 103, 109, 127, 163, 193, 223, 229, 277, 307, 313, 349, 379, 397, 439, 457, 463, 487, 499, 613, 643, 673, 739, 757, 769, 823, 853, 859, 877, 883, 907, 937, 967, 1009, 1087, 1093, 1213, 1279, 1297, 1303, 1423 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This sequence contains the composite number 305635357, so is different from A023200 and A029710 (305635357 is the only composite member of the present sequence below 10^9). - Jud McCranie, Jan 07 2001 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 MATHEMATICA Select[Range[1500], DivisorSigma[1, #]+4==DivisorSigma[1, #+4]&] (* Harvey P. Dale, Nov 04 2011 *) PROG (PARI) is(n)=sigma(n)+4==sigma(n+4) \\ Charles R Greathouse IV, Mar 09 2014 CROSSREFS Cf. A023200, A029710. Sequence in context: A216518 A342822 A154650 * A023200 A046136 A098044 Adjacent sequences: A015910 A015911 A015912 * A015914 A015915 A015916 KEYWORD nonn AUTHOR Robert G. Wilson v STATUS approved

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Last modified May 18 15:58 EDT 2024. Contains 372664 sequences. (Running on oeis4.)