

A034884


n < d(n)^2, d() = number of divisors.


31



2, 3, 4, 6, 8, 10, 12, 14, 15, 16, 18, 20, 24, 28, 30, 32, 36, 40, 42, 48, 54, 56, 60, 72, 80, 84, 90, 96, 108, 120, 126, 132, 140, 144, 168, 180, 192, 210, 216, 240, 252, 288, 300, 336, 360, 420, 480, 504, 540, 720, 840, 1260
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

See comment in A175495.  Vladimir Shevelev, May 07 2013
The deficient terms are 2, 3, 4, 8, 10, 14, 15, 16, 32; the first perfect or abundant number not listed is 66 = 2 * 3 * 11; the only term not 7smooth is 132 = 2^2 * 3 * 11; the largest not divisible by 6 is 140 = 2^2 * 5 * 7.  Peter Munn, Sep 19 2021


LINKS

Table of n, a(n) for n=1..52.


MATHEMATICA

Select[Range[1300], #<DivisorSigma[0, #]^2&] (* Harvey P. Dale, Apr 11 2014 *)


PROG

(PARI) isok(n) = (n < numdiv(n)^2) \\ Michel Marcus, Jun 07 2013


CROSSREFS

Cf. A000005, A035033, A035034, A035035, A033950, A036763.
Sequence in context: A336367 A064377 A175495 * A137291 A032954 A158023
Adjacent sequences: A034881 A034882 A034883 * A034885 A034886 A034887


KEYWORD

nonn,fini,full


AUTHOR

Erich Friedman


EXTENSIONS

Labos Elemer added the last three terms and observes that this sequence is now complete.


STATUS

approved



