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Sliding numbers which are products of three distinct primes.
0

%I #16 Oct 09 2022 15:45:59

%S 70,110,290,1001,1010,1258,3157,3445,5002,6266,6410,50002,1958245,

%T 2000005,9766649,9775865,20000005,48830173,200000005,488283298,

%U 2000000005,2441410346,6103679465,10000000001,12207039442,30517905805,50000000002,61035172634,152588545985,200000000005,305175814018

%N Sliding numbers which are products of three distinct primes.

%C A squarefree subsequence of numbers of the form p + q where 1/p + 1/q = (p + q)/10^k for some k >= 1.

%e 70 = 2*5*7 (70 = 20 + 50 and 1/20 + 1/50 = 0.070).

%e 1001 = 7*11*13 (1001 = 1 + 1000 and 1/1 + 1/1000 = 1.001).

%e 9766649 = 29*61*5521 (9766649 = 1024 + 9765625 and 1/1024 + 1/9765625 = 0.0009766649).

%e 200000005 = 5*53*754717 (200000005 = 5 + 200000000 and 1/5 + 1/200000000 = 0.200000005).

%Y Intersection of A103182 and A007304.

%K nonn,base

%O 1,1

%A _Massimo Kofler_, Oct 08 2022

%E More terms from _Hugo Pfoertner_, Oct 08 2022