

A295075


Numbers k such that d + k/d is never prime for any divisor d of k.


2



3, 5, 7, 8, 9, 11, 13, 14, 15, 17, 19, 20, 21, 23, 25, 26, 27, 29, 31, 32, 33, 35, 37, 38, 39, 41, 43, 44, 45, 47, 49, 50, 51, 53, 55, 56, 57, 59, 61, 62, 63, 64, 65, 67, 68, 69, 71, 73, 74, 75, 77, 79, 80, 81, 83, 85, 86, 87, 89, 91, 92, 93, 94, 95, 97, 98, 99
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OFFSET

1,1


COMMENTS

Numbers k such that A282849(k) = 0.


LINKS

Robert Israel, Table of n, a(n) for n = 1..10000


MAPLE

remove(n > ormap(t > isprime(t+n/t), numtheory:divisors(n)), [$1..100]); # Robert Israel, Nov 14 2017


MATHEMATICA

Select[Range@ 100, Function[k, NoneTrue[Divisors@ k, PrimeQ[# + k/#] &]]] (* Michael De Vlieger, Nov 13 2017 *)


PROG

(PARI) isok(n) = sumdiv(n, d, isprime(d+n/d)) == 0;


CROSSREFS

Cf. A282849 (number of divisors of n such that d + n/d is prime), A080715 (d + n/d is prime for every divisor d of n).
Includes all elements > 2 of A047255.
Sequence in context: A249433 A300737 A062958 * A184996 A153309 A047486
Adjacent sequences: A295072 A295073 A295074 * A295076 A295077 A295078


KEYWORD

nonn


AUTHOR

Michel Marcus, Nov 13 2017


STATUS

approved



