A164768 - OEIS

%I #8 Feb 08 2020 04:07:06

%S 1,2,1,3,2,6,4,5,7,8,10,14,16,20,25,3,32,40,50,6,64,80,100,12,113,15,

%T 160,200,24,226,30,320,400,48,452,60,565,75,800,96,904,120,1130,150,

%U 1600,192,1808,240,2260,300,2825,375,384,3616,480,4520,600,5650

%N First differences of A003592.

%C The gaps between the natural numbers whose reciprocals are terminating decimals.

%H Amiram Eldar, <a href="/A164768/b164768.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..312 from Barry Wells)

%F a(n) = A003592(n+1) - A003592(n). - _Amiram Eldar_, Feb 08 2020

%e The first few terms of A003592 are 1, 2, 4, 5, 8, 10, 16 because 1/1, 1/2, 1,4, 1/5, 1/8 etc. terminate and 1/3, 1/6, 1/7, 1/9 etc. repeat. Hence the denominators of the first few terminating decimals are 1, 2, 4, 5, 8, 10, 16 and the first differences between these gives the sequence 1,2,1,3,2,4

%Y Cf. A003592.

%K nonn

%O 1,2

%A Barry Wells (wells.barry(AT)gmail.com), Aug 26 2009, Sep 24 2009