

A093894


Composite members of A093893.


2



49, 87, 91, 121, 133, 169, 183, 213, 217, 247, 249, 259, 287, 301, 339, 343, 361, 403, 411, 427, 445, 469, 473, 481, 501, 511, 527, 529, 553, 559, 581, 589, 591, 633, 679, 699, 703, 713, 717, 721, 763, 789, 793, 817, 841, 843, 871, 889, 895, 949, 951, 961
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OFFSET

1,1


COMMENTS

Comment: Most terms of this sequence have four divisors. Some terms (the squares of primes) have three divisors; very few terms have more than four divisors (the first such term is 4753, with six). Conjecture: This sequence is infinite.  Adam M. Kalman (mocha(AT)clarityconnect.com), Nov 11 2004


LINKS



EXAMPLE

133 is a term, the divisors are 1,7,19,133 and no sum of two or more gives a prime.


MATHEMATICA

For[a:=4, a<=2000, s =Divisors[a]; n := 1; d := False; While[(n<=2^Length[s])\[And]( ["not" character]d), If[Length[NthSubset[n, s]]>=2, If[ !PrimeQ[Plus@@NthSubset[n, s]], n++, d:= True], n++ ]]; If[ ["not" character]d, Print[a]]; a++; While[PrimeQ[a], a+=2]]; (* Adam M. Kalman, Nov 11 2004 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



EXTENSIONS

Corrected and extended by Adam M. Kalman (mocha(AT)clarityconnect.com), Nov 11 2004


STATUS

approved



