A093894 Composite members of A093893.

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

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