|
Search: id:A063640
|
|
|
| A063640 |
|
Primes of form p*q*r + 1, where p, q and r are primes. |
|
+0
4
|
|
| 13, 19, 29, 31, 43, 53, 67, 71, 79, 103, 131, 139, 149, 173, 191, 223, 239, 269, 283, 293, 311, 317, 367, 389, 419, 431, 439, 443, 499, 509, 557, 599, 607, 619, 643, 647, 653, 659, 683, 743, 773, 787, 797, 823, 827, 907, 947, 971, 1031, 1039, 1087, 1091
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
Also semiprimes of the form (p-1)/2 where p is a prime. - Robert G. Wilson v Sep 01 2007.
|
|
MATHEMATICA
|
Take[ Select[ Union@ Flatten@ Table[ Prime@p*Prime@q*Prime@r + 1, {p, 48}, {q, p}, {r, q}], PrimeQ@ # &], 53] (* Or *)
semiPrimeQ[x_] := Plus @@ Last /@ FactorInteger[x] == 2; Select[Prime@ Range@ 182, semiPrimeQ[(# - 1)/2] &] (* Robert G. Wilson v (rgwv@rgwv.com), Sep 01 2007 *)
|
|
CROSSREFS
|
Cf. A014612, A063639.
Adjacent sequences: A063637 A063638 A063639 this_sequence A063641 A063642 A063643
Sequence in context: A109902 A058898 A123840 this_sequence A092104 A094105 A073620
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jul 21 2001
|
|
|
Search completed in 0.002 seconds
|
