A236107 Nonprimes whose divisors are partition numbers.

1, 15, 22, 77

Offset

1,2

Comments

By definition all terms are partition numbers.

Conjecture: no terms exist beyond 77. - Jon E. Schoenfield, Feb 05 2014

Links

Table of n, a(n) for n=1..4.

Example

15 is in the sequence because 15 is a nonprime number and the divisors of 15 are 1, 3, 5, 15, which are also partition numbers.

Mathematica

nmax = 1000;
pp = PartitionsP[Range[nmax]];
selQ[n_] := Module[{dd = Divisors[n]}, Intersection[pp, dd] == dd];
Select[Range[nmax], !PrimeQ[#] && selQ[#]&] (* Jean-François Alcover, Apr 09 2020 *)

Crossrefs

Cf. A000041, A018252, A038753, A236102, A236103, A236105, A236108, A236110.

Sequence in context: A109288 A018889 A186525 * A065728 A344134 A241253

Adjacent sequences: A236104 A236105 A236106 * A236108 A236109 A236110

Keyword

nonn,more

Author

Omar E. Pol, Jan 22 2014

Status

approved