

A208767


Generalized 2super abundant numbers.


2



1, 2, 4, 6, 12, 24, 48, 60, 120, 240, 360, 720, 840, 1680, 2520, 5040, 10080, 15120, 25200, 27720, 55440, 110880, 166320, 277200, 332640, 360360, 720720, 1441440, 2162160, 3603600, 4324320, 7207200, 10810800, 12252240, 21621600, 24504480, 36756720, 61261200
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OFFSET

1,2


COMMENTS

The generalized ksuper abundant numbers are those such that sigma_k(n)/(n^k) > sigma_k(m)/(m^k) for all m < n, where sigma_k(n) is the sum of the kth powers of the divisors of n.
1super abundant numbers are A004394. 0super abundant numbers are A002182.
Pillai called these numbers "highly abundant numbers of the 2nd order".  Amiram Eldar, Jun 30 2019


LINKS

Amiram Eldar, Table of n, a(n) for n = 1..251
S. Sivasankaranarayana Pillai, Highly abundant numbers, Bulletin of the Calcutta Mathematical Society, Vol. 35, No. 1 (1943), pp. 141156.
S. Sivasankaranarayana Pillai, On numbers analogous to highly composite numbers of Ramanujan, Rajah Sir Annamalai Chettiar Commemoration Volume, ed. Dr. B. V. Narayanaswamy Naidu, Annamalai University, 1941, pp. 697704.
Srinivasa Ramanujan, Highly composite numbers, Annotated and with a foreword by JeanLouis Nicolas and Guy Robin, The Ramanujan Journal, Vol. 1, No. 2 (1997), pp. 119153, alternative link.


EXAMPLE

For i=24, sigma_2(24)/(24^2)=850/576=1.47569, a new record, thus 24 is in the sequence.


MATHEMATICA

s = {1}; a = 1; Do[ If[DivisorSigma[2, n]/(n^2) > a, a = DivisorSigma[2, n]/(n^2); AppendTo[s, n]], {n, 10000000}]; s


CROSSREFS

Cf. A002182, A004394, A004490, A002201, A001157.
Subsequence of A025487.
Sequence in context: A047151 A068010 A095848 * A136339 A019505 A135614
Adjacent sequences: A208764 A208765 A208766 * A208768 A208769 A208770


KEYWORD

nonn


AUTHOR

Ben Branman, Mar 01 2012


EXTENSIONS

More terms from Amiram Eldar, May 12 2019


STATUS

approved



