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Search: id:A093894
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| 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
(list; graph; listen)
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OFFSET
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0,1
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COMMENT
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Comment: Most terms of this sequence have four divisors. Some (the prime squares) have three divisors, and very few terms have more than four divisors (the first one is 4753, with six). Conjecture: This sequence is infinite. - Adam M. Kalman (mocha(AT)clarityconnect.com), Nov 11 2004
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EXAMPLE
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133 is a member, the divisors are 1,7,19,133 and no sum of two or more gives a prime.
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MATHEMATICA
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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]]; (Kalman)
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CROSSREFS
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Cf. A093890, A093891, A093892, A093893.
Sequence in context: A056938 A106311 A006832 this_sequence A090825 A118886 A108164
Adjacent sequences: A093891 A093892 A093893 this_sequence A093895 A093896 A093897
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KEYWORD
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nonn
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AUTHOR
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Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Apr 23 2004
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EXTENSIONS
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Corrected and extended by Adam M. Kalman (mocha(AT)clarityconnect.com), Nov 11 2004
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