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A236107
Nonprimes whose divisors are partition numbers.
6
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
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 *)
KEYWORD
nonn,more
AUTHOR
Omar E. Pol, Jan 22 2014
STATUS
approved