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A078664 Number of divisors of the n-th Ulam number. 1

%I

%S 1,2,2,3,4,4,2,2,5,6,4,6,9,4,2,10,2,4,4,4,12,4,4,4,2,6,8,4,8,12,2,8,4,

%T 6,4,6,4,18,8,8,2,4,4,4,4,6,8,2,6,4,8,12,8,8,4,6,4,15,4,4,6,4,6,8,4,

%U 16,15,8,2,6,12,8,2,8,9,4,16,8,4,4,4,12,6

%N Number of divisors of the n-th Ulam number.

%H Amiram Eldar, <a href="/A078664/b078664.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = A000005(A002858(n)). - _Amiram Eldar_, Sep 29 2019

%t u = {1, 2, 3, 4, 6, 8, 11, 13, 16, 18, 26, 28, 36, 38, 47, 48, 53, 57, 62, 69, 72, 77, 82, 87, 97, 99, 102, 106, 114, 126, 131, 138, 145, 148, 155, 175, 177, 180, 182, 189, 197, 206, 209, 219, 221, 236, 238, 241, 243, 253, 258, 260, 273, 282, 309, 316, 319, 324, 339}; Table[DivisorSigma[0, u[[n]]], {n, 1, 50}]

%Y Cf. A000005, A002858.

%K easy,nonn

%O 1,2

%A _Joseph L. Pe_, Dec 15 2002

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Last modified August 11 09:47 EDT 2020. Contains 336423 sequences. (Running on oeis4.)