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A112276 Smallest number greater than n having no more divisors than n; a(1) = 1. 4

%I #13 Feb 03 2020 03:50:06

%S 1,3,5,5,7,7,11,9,11,11,13,13,17,15,17,17,19,19,23,21,22,23,29,25,29,

%T 27,29,29,31,31,37,33,34,35,37,37,41,39,41,41,43,43,47,45,46,47,53,49,

%U 53,51,53,53,59,55,57,57,58,59,61,61,67,65,65,65,67,67,71,69,71,71,73,73

%N Smallest number greater than n having no more divisors than n; a(1) = 1.

%H Amiram Eldar, <a href="/A112276/b112276.txt">Table of n, a(n) for n = 1..10000</a>

%F A000005(a(n)) <= A000005(n) and A000005(k) > A000005(n) for n < k < a(n).

%t a[1] = 1; a[n_] := Module[{m = n+1, d=DivisorSigma[0, n]}, While[DivisorSigma[0, m] > d, m++]; m]; Array[a, 100] (* _Amiram Eldar_, Feb 03 2020 *)

%Y A065091 (the odd primes) is a subsequence.

%Y See A112277 for numbers m such that a(m) is composite.

%Y Cf. A000005, A065091.

%Y Cf. A079427, A112275.

%K nonn

%O 1,2

%A _Reinhard Zumkeller_, Sep 01 2005

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Last modified March 29 03:51 EDT 2024. Contains 371264 sequences. (Running on oeis4.)