A240164 Numbers n such that (k!+n)/k and (k!-n)/k are prime for some k.

4, 25, 35, 42, 65, 66, 85, 95, 102, 114, 121, 133, 152, 170, 186, 204, 222, 259, 279, 282, 296, 318, 328, 333, 354, 366, 376, 438, 451, 462, 469, 474, 536, 539, 546, 583, 584, 603, 618, 623, 642, 654, 678, 682, 707, 721, 749, 833, 856, 931, 938, 963, 1001, 1048, 1062, 1079, 1099, 1141

Offset

1,1

Comments

Subsequence of intersection of A240161 and A240163. [Corrected by Jens Kruse Andersen, Aug 04 2014]

By using Wilson's theorem, we can show that each term of the sequence is composite. - Farideh Firoozbakht, Aug 02 2014

Links

Table of n, a(n) for n=1..58.

Prog

(PARI)
a(n)=for(k=1, n, s=(k!+n)/k; t=(k!-n)/k; if(floor(s)==s&&floor(t)==t, if(ispseudoprime(s)&&ispseudoprime(t), return(k))))
n=1; while(n<10^3, if(a(n), print1(n, ", ")); n++)

Crossrefs

Cf. A240161, A240163.

Sequence in context: A303183 A175052 A370575 * A169600 A267765 A231176

Adjacent sequences: A240161 A240162 A240163 * A240165 A240166 A240167

Keyword

nonn

Author

Derek Orr, Aug 01 2014

Status

approved