A240163 -id:A240163 - cp's OEIS frontend

A240161 Numbers n such that (k!-n)/k is prime for some k.

4, 5, 7, 8, 12, 13, 15, 16, 25, 31, 33, 34, 35, 39, 42, 55, 65, 66, 77, 78, 85, 95, 102, 105, 110, 114, 121, 130, 133, 136, 138, 152, 156, 167, 169, 170, 186, 187, 203, 204, 221, 222, 232, 246, 248, 253, 255, 259, 279, 282, 290, 294, 296, 301, 318, 322, 325, 328, 329, 333, 354, 366

Offset: 1

Derek Orr, Aug 01 2014

nonn

Numbers n such that A240160(n) is not null. - Michel Marcus, Aug 05 2014

Jens Kruse Andersen, Table of n, a(n) for n = 1..300

Cf. A240160, A240163.

a(n)=for(k=1,n,s=(k!-n)/k;if(floor(s)==s,if(ispseudoprime(s),return(k))))
n=1;while(n<500,if(a(n),print1(n,", "));n++)

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

Original entry on oeis.org

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

Derek Orr, Aug 01 2014

nonn

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

Cf. A240161, A240163.

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++)

cp's OEIS Frontend

A240161 Numbers n such that (k!-n)/k is prime for some k.

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