A121387 Semiprimes p*q with p and q primes of the form 4k+1 (A002144).

25, 65, 85, 145, 169, 185, 205, 221, 265, 289, 305, 365, 377, 445, 481, 485, 493, 505, 533, 545, 565, 629, 685, 689, 697, 745, 785, 793, 841, 865, 901, 905, 949, 965, 985, 1037, 1073, 1145, 1157, 1165, 1189, 1205, 1241, 1261, 1285, 1313, 1345, 1369, 1385, 1405, 1417

Offset: 1

Author

Alford Arnold, Jul 26 2006, corrected Jun 24 2007

Keywords

• easy
• nonn

Comments

p and q can be the same. [Harvey P. Dale, Jan 15 2012]

The terms are semiprimes of the form 4k + 1, and comprise only a portion of all such semiprimes, see A108181. - Richard R. Forberg, Aug 27 2013

Examples

			65 = 5 * 13. Note that 5 mod 4 = 1 and 13 mod 4 = 1, so 65 is a term.
		

Links

• François Huppé, Table of n, a(n) for n = 1..10000 (First 1000 terms from T. D. Noe).

Crossrefs

Cf. A001358, A002144.

Fifth row of A121388.

Union of A080109 and A131574.

Cf. A107978, A080774, A108181.

Programs

Mathematica

With[{prs=Select[Prime[Range[150]],Mod[#,4]==1&]},Take[Union[Times @@@ Tuples[prs,2]],60]] (* Harvey P. Dale, Jan 15 2012 *)

Extensions

Better definition from T. D. Noe, Sep 25 2007