# [seqfan] Re: Missing word in A107978

Jonathan Post jvospost3 at gmail.com
Fri May 21 09:59:46 CEST 2010

```That's fine.  Thank you, Dr. Neil J. A. Sloane, for your edit to the
revision as below.

For the record, I admit mistakes.  Every teacher makes them; I give my
students extra credit for correcting me in the classroom. Marc LeBrun
is right, too. I have, in fact, sold articles to encyclopedias, such
as the Gale Encyclopedia of Computer Science.  And I have provided 19
entries or contributions to my Caltech co-alumnus Eric W. Weisstein,
for his MathWorld--A Wolfram Web Resource. And knew Wolfram since he
was a Physics professor at Caltech.  So no need to scold me, anyone.
Almost everyone slips at times. "Even Homer nods." .  Neil J. A.
Sloane and his wonderful Associate Editors have caught errors of mine
before, and doubtless others remain here and there among the 2541
sequences in OEIS to which I've contributed.  This is a collaborative
system, and every writer (Math or otherwise) appreciates good editing.
Thank you to everyone who has helped in that capacity.

Best,

Prof. Jonathan Vos Post

A107978  	 	 Products of two primes of the form 4n+3 (A002145).

9, 21, 33, 49, 57, 69, 77, 93, 121, 129, 133, 141, 161, 177, 201, 209,
213, 217, 237, 249, 253, 301, 309, 321, 329, 341, 361, 381, 393, 413,
417, 437, 453, 469, 473, 489, 497, 501, 517, 529, 537, 553, 573, 581,
589, 597, 633, 649, 669, 681, 713, 717, 721, 737 (list; graph; listen)

OFFSET
1,1

COMMENT
Every odd semiprime must be in one of three disjoint sets: the product
of two primes of the form 4n+1, the product of two primes of the form
4n+3, or the product of a prime of the form 4n+1 and a prime of the
form 4n+3.

T. D. Noe, Table of n, a(n) for n=1..1000

Eric Weisstein's World of Mathematics, Semiprime.

FORMULA
{a(n)} = {p*q: p and q both elements of A002145}.

CROSSREFS

Cf. A001358, A002145.

Cf. A080774, A121387 (the other two sets of odd semiprimes)

Sequence in context: A133929 A086470 A017629 this_sequence A043112
A043892 A146069

Adjacent sequences: A107975 A107976 A107977 this_sequence A107979
A107980 A107981

KEYWORD
easy,nonn,new

AUTHOR
Jonathan Vos Post (jvospost3(AT)gmail.com), Jun 12 2005

EXTENSIONS
Edited by N. J. A. Sloane, May 20 2010

On Thu, May 20, 2010 at 9:03 PM, N. J. A. Sloane <njas at research.att.com> wrote:
> Thanks for the comments on that sequence.  I have
> made a number of editorial changes to it.
>
> Neil
>
> _______________________________________________
>
> Seqfan Mailing list - http://list.seqfan.eu/

```