|
| |
|
|
A108181
|
|
Semiprimes of the form 4n + 1.
|
|
3
|
|
|
|
9, 21, 25, 33, 49, 57, 65, 69, 77, 85, 93, 121, 129, 133, 141, 145, 161, 169, 177, 185, 201, 205, 209, 213, 217, 221, 237, 249, 253, 265, 289, 301, 305, 309, 321, 329, 341, 361, 365, 377, 381, 393, 413, 417, 437, 445, 453, 469, 473, 481, 485, 489, 493, 497
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
COMMENTS
|
Either a(n)=(4*i+1)*(4*j+1) or a(n)=(4*i+3)*(4*j+3); - Reinhard Zumkeller, Jun 15 2005
A107978 is a subsequence. - Reinhard Zumkeller, Jun 15 2005
|
|
|
LINKS
|
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
K. Ford, Jason Sneed, Chebyshev's Bias for products of two primes, Exper. Math. 19 (4) (2010) 385-398
|
|
|
MATHEMATICA
|
Select[4Range[0, 150] + 1, PrimeOmega[#] == 2&] (* Vincenzo Librandi, Sep 22 2012 *)
|
|
|
PROG
|
(MAGMA) IsSemiprime:= func<n | &+[d[2]: d in Factorization(n)] eq 2>; [s: n in [2..150] | IsSemiprime(s) where s is 4*n + 1]; // Vincenzo Librandi, Sep 22 2012
|
|
|
CROSSREFS
|
Cf. A080774, A001358, A002144, A002145.
Sequence in context: A143791 A091113 A188159 * A173456 A192192 A053795
Adjacent sequences: A108178 A108179 A108180 * A108182 A108183 A108184
|
|
|
KEYWORD
|
easy,nonn
|
|
|
AUTHOR
|
Giovanni Teofilatto, Jun 14 2005
|
|
|
EXTENSIONS
|
Corrected and extended by Reinhard Zumkeller, Jun 15 2005
|
|
|
STATUS
|
approved
|
| |
|
|
