|
| |
|
|
A115404
|
|
Numbers n such that n^4+1 is a 4-almost prime (product of four primes).
|
|
0
| |
|
|
43, 59, 77, 79, 83, 85, 95, 111, 127, 137, 147, 155, 178, 179, 185, 202, 221, 223, 227, 229, 233, 239, 241, 247, 249, 253, 261, 263, 270, 271, 273, 285, 287, 297, 314, 331, 338, 341, 342, 357, 359, 387, 389, 393, 395, 401, 408, 413, 421, 427, 433, 435, 437
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
FORMULA
| n^4+1=p*q*r*s where p, q, r, s are primes (not necessarily distinct).
|
|
|
EXAMPLE
| 43 is OK because 43^4+1=3418802=2*17*193*521 (product of four primes).
|
|
|
MATHEMATICA
| Select[Range[500], Sum[FactorInteger[ #^4 + 1][[i]][[2]], {i, 1, Length[FactorInteger[ #^4 + 1]]}] == 4 &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Mar 09 2006
|
|
|
CROSSREFS
| Cf. A014613 = 4-almost primes.
Sequence in context: A166491 A127880 A078132 * A033223 A064508 A102540
Adjacent sequences: A115401 A115402 A115403 * A115405 A115406 A115407
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Zak Seidov (zakseidov(AT)yahoo.com), Mar 08 2006
|
| |
|
|
