1,2

Amiram Eldar, Table of n, a(n) for n = 1..10000

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

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 *)

A065091 (the odd primes) is a subsequence.

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

Cf. A000005, A065091.

Cf. A079427, A112275.

Sequence in context: A309424 A079886 A087243 * A079578 A066169 A242189

Adjacent sequences: A112273 A112274 A112275 * A112277 A112278 A112279

nonn

Reinhard Zumkeller, Sep 01 2005

approved