The On-Line Encyclopedia of Integer Sequences (OEIS)

Revisions by Emmanuel Vantieghem (See also Emmanuel Vantieghem's wiki page)

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
Showing entries 1-10 | older changes

A112386

Smallest prime obtained by appending one or more 1's to n, -1 if no such prime exists.
(history; published version)

#11 by Emmanuel Vantieghem at Thu Oct 27 08:35:13 EDT 2022

STATUS

editing

proposed

#10 by Emmanuel Vantieghem at Thu Oct 27 08:33:30 EDT 2022

NAME

Smallest prime obtained by appending one or more 1's to n, -1 if no such prime exists.

COMMENTS

a(37) = -1 since there is a covering of the set {371,3711,37111,...} by the prime moduli 3, 7, 13, 37. Hence, there are infinitely many values -1 in the sequence (at 371, 3711, 37111 ...).

EXTENSIONS

Edited, corrected and extended by Emmanuel Vantieghem, Oct 27 2022

STATUS

approved

editing

Discussion

Thu Oct 27

08:35

Emmanuel Vantieghem: a(38)  is also -1 but there is a more sophisticated reason for that.

A078840

Table of n-almost-primes T(n,k) (n >= 0, k > 0), read by antidiagonals, starting at T(0,1)=1 followed by T(1,1)=2.
(history; published version)

#57 by Emmanuel Vantieghem at Sat Aug 06 05:16:25 EDT 2022

STATUS

editing

proposed

#55 by Emmanuel Vantieghem at Fri Jul 29 09:58:15 EDT 2022

MATHEMATICA

(* The next code skips the initial 1.*)

STATUS

approved

editing

Discussion

Fri Jul 29

10:00

Emmanuel Vantieghem: This is only a very small correction : ommitting the "*" makes the program unworkable.

A278837

Primes p such that the ring of algebraic integers of Q(sqrt(p)) does not have unique factorization.
(history; published version)

#24 by Emmanuel Vantieghem at Fri Mar 08 14:38:20 EST 2019

STATUS

editing

proposed

#23 by Emmanuel Vantieghem at Fri Mar 08 14:38:07 EST 2019

EXTENSIONS

Missing term 2089 added by _Emmanuel Vantieghem_, Mar 08 2019

#21 by Emmanuel Vantieghem at Fri Mar 08 11:47:42 EST 2019

STATUS

editing

proposed

Discussion

Fri Mar 08

11:50

Michel Marcus: no please remove Emmanuel Vantieghem, and system will fill name and date

#20 by Emmanuel Vantieghem at Fri Mar 01 04:05:20 EST 2019

EXTENSIONS

Missing term 2089 added by Emmanuel Vantieghem

Discussion

Fri Mar 08

09:50

OEIS Server: This sequence has not been edited or commented on for a week
yet is not proposed for review.  If it is ready for review, please
visit https://oeis.org/draft/A278837 and click the button that reads
"These changes are ready for review by an OEIS Editor."

Thanks.
  - The OEIS Server

#16 by Emmanuel Vantieghem at Thu Feb 28 16:44:34 EST 2019

STATUS

editing

proposed

Discussion

Fri Mar 01

00:25

Michel Marcus: please add an extension for new term

#15 by Emmanuel Vantieghem at Thu Feb 28 16:41:21 EST 2019

DATA

79, 223, 229, 257, 359, 401, 439, 443, 499, 577, 659, 727, 733, 761, 839, 1009, 1087, 1091, 1093, 1129, 1171, 1223, 1229, 1297, 1327, 1367, 1373, 1429, 1489, 1523, 1567, 1601, 1627, 1787, 1811, 1847, 1901, 1907, 1987, 2027, 2029, 2081, 2089, 2099, 2143, 2153, 2207, 2213, 2251, 2399, 2459, 2467

STATUS

approved

editing

Discussion

Thu Feb 28

16:44

Emmanuel Vantieghem: I added the term 2089 (it is prime and the corresponding class number is 3).
It appeared after I runned the Mathematica program.