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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
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
Sequence in context: A216518 A342822 A154650 * A023200 A046136 A098044
KEYWORD
nonn
AUTHOR
STATUS
approved

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