A121387 - OEIS

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

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OFFSET

1,1

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

LINKS

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

EXAMPLE

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

MATHEMATICA

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

CROSSREFS

Cf. A001358, A002144.

Fifth row of A121388.

Union of A080109 and A131574.

Cf. A107978, A080774, A108181.

Sequence in context: A120961 A285579 A050993 * A039376 A043199 A043979

Adjacent sequences: A121384 A121385 A121386 * A121388 A121389 A121390

KEYWORD

easy,nonn

AUTHOR

Alford Arnold, Jul 26 2006, corrected Jun 24 2007

EXTENSIONS

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

STATUS

approved