A190299 Squarefree semiprimes of the form 4k+1.

21, 33, 57, 65, 69, 77, 85, 93, 129, 133, 141, 145, 161, 177, 185, 201, 205, 209, 213, 217, 221, 237, 249, 253, 265, 301, 305, 309, 321, 329, 341, 365, 377, 381, 393, 413, 417, 437, 445, 453, 469, 473, 481, 485, 489, 493, 497, 501, 505, 517, 533, 537, 545

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, May 07 2011

Keywords

• nonn

Comments

There are 961 squarefree semiprimes of the form 4k+1 below 10000.

Links

• T. D. Noe, Table of n, a(n) for n = 1..1000
• Eric Weisstein's World of Mathematics, Semiprime
• Wikipedia, Semiprime

Crossrefs

Cf. A001358, A006881, A080774. Union of A131574 and A016105.

Programs

Mathematica

Select[Range[1,600,4],Last/@FactorInteger[#]=={1,1}&]

Extensions

Edited by Ray Chandler, Dec 16 2011