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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 (list; graph; refs; listen; history; text; internal format)
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

Charles R. Greathouse IV, Sep 10, 2008, Table of n, a(n) for n = 1..10001

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

Cf. A093890, A093891, A093892, A093893.

Sequence in context: A343022 A250074 A247678 * A259766 A273937 A326257

Adjacent sequences: A093891 A093892 A093893 * A093895 A093896 A093897

KEYWORD

nonn

AUTHOR

Amarnath Murthy, Apr 23 2004

EXTENSIONS

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

STATUS

approved

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Last modified November 29 18:13 EST 2022. Contains 358431 sequences. (Running on oeis4.)