A245027 - OEIS

%I #19 Sep 08 2022 08:46:08

%S 1,2,3,4,5,6,8,9,10,12,13,15,16,18,19,20,24,25,26,30,32,36,38,39,40,

%T 43,45,48,50,52,57,60,65,72,75,76,78,80,86,90,95,96,100,104,114,117,

%U 120,129,130,144,150,152,156,160,171,172,180,181,190,195,200,208

%N Divisors of 7^12 - 1.

%C Number of divisors of k^12-1 for k = 2..20: 24 (2), 80 (3), 96 (4), 240 (5), 128 (6), 864 (7), 512 (8), 384 (9), 256 (10), 1920 (11), 256 (12), 960 (13), 384 (14), 448 (15), 768 (16), 1792 (17), 768 (18), 3840 (19), 384 (20).

%C The following triangular numbers belong to this sequence: 1, 3, 6, 10, 15, 36, 45, 78, 120, 171, 190, 300, 325, 741, 780, 2080, 2850, 4560, 8385, 14706, 16290, 5915080, 1730160900.

%H Bruno Berselli, <a href="/A245027/b245027.txt">Table of n, a(n) for n = 1..864</a>

%H <a href="/index/Di#divisors">Index entries for sequences related to divisors of numbers</a>

%e 13841287200 = 2^5 * 3^2 * 5^2 * 13 * 19 * 43 * 181.

%t Divisors[7^12 - 1]

%o (PARI) divisors(7^12-1)

%o (Sage) divisors(7^12-1)

%o (Magma) Divisors(7^12-1);

%o (Maxima) divisors(7^12-1);

%Y Cf. Divisors of k^12-1: A003524 (k=2); A003532 (k=4); A003543 (k=8), A027902 (k=9), A027897 (k=10), A245028 (k=11).

%K nonn,fini,full

%O 1,2

%A _Bruno Berselli_, Jul 10 2014