login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A316887 Numbers k whose partition numbers have more than k nontrivial divisors. 0

%I #18 Jul 30 2018 13:21:35

%S 21,75,94,96,97,109,124,125,128,129,131,136,149,180,213,327,334,347,

%T 358,374,424,434,449,481,581,644,699,765,776,789,859,896,974,999,1216,

%U 1240,1243,1249,1267,1269,1324,1398,1442,1499,1524,1587,1685,1699,1752,1779

%N Numbers k whose partition numbers have more than k nontrivial divisors.

%e 21 belongs to this sequence as the partition number of 21 is 792, which has 22 nontrivial divisors (divisors different from 1 and itself), and 22 > 21.

%t Select[Range[1000], DivisorSigma[0, PartitionsP[#]] > # + 2 &] (* or *) First/@ Select[ Import[ "https://oeis.org/A085543/b085543.txt", "Table"], #[[2]] > #[[1]] + 2&] (* _Giovanni Resta_, Jul 16 2018 *)

%o (PARI) select(n->numdiv(numbpart(n))-2 > n, [1..1000]) \\ _Andrew Howroyd_, Jul 15 2018

%o (Sage)

%o r=""

%o for i in range(1000):

%o l=Partitions(i+1).cardinality().divisors()

%o if ((len(l)-2)>i+1): r=r+str(i+1)+","

%o print(r)

%Y Cf. A000005, A000041, A085543.

%K nonn

%O 1,1

%A _Pierandrea Formusa_, Jul 15 2018

%E a(35)-a(50) from _Giovanni Resta_, Jul 16 2018

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified April 23 07:34 EDT 2024. Contains 371905 sequences. (Running on oeis4.)