|
%I #12 Aug 03 2016 09:17:01
%S 0,2,5,7,9,12,14,16,21,23,39,48,55,60,62,225,264,273,280,285,287,440,
%T 615,665,672,704,713,720,725,727,945,952,1080,1368,1392,1536,1560,
%U 1617,1656,1665,1672,1677,1679,1695,1800,2040,2112,2280,2328,2337,2376,2385
%N Numbers n >= 0 such that there exists a number m with sigma(m) and sigma(m+n) both prime.
%C Nonnegative numbers of the form A023194(i) - A023194(j). - _Altug Alkan_, Jul 22 2016
%H Chai Wah Wu, <a href="/A275278/b275278.txt">Table of n, a(n) for n = 1..10000</a>
%e 5 is a term since sigma(4) = 7 and sigma(9) = 13 are both prime.
%e 2385 is a term since sigma(16) = 31 and sigma(2401) = 2801 are both prime.
%t Select[Range[0, 10^3], Function[n, Total@ Boole@ Map[And[PrimeQ@ DivisorSigma[1, #], PrimeQ@ DivisorSigma[1, # + n]] &, Range[10 n]] > 0]] (* _Michael De Vlieger_, Jul 22 2016 *)
%Y Cf. A023194.
%K nonn
%O 1,2
%A _Chai Wah Wu_, Jul 21 2016
|
