The On-Line Encyclopedia of Integer Sequences (OEIS)

Revisions by N. J. A. Sloane

(See also N. J. A. Sloane's wiki page
and changes approved by N. J. A. Sloane)

(Bold, blue-underlined text is an addition; faded, red-underlined text is a ~~deletion~~.)
newer changes | Showing entries 11-20 | older changes

A050414

Numbers k such that 2^k - 3 is prime.
(history; published version)

#74 by N. J. A. Sloane at Sat Feb 01 14:10:39 EST 2025

CROSSREFS

Cf. Sequences of numbers k such that 2^k - d is prime: A000043 (d=1), A050414 (d=3), A059608 (d=5), A059609 (d=7), A059610 (d=9), A096817 (d=11), A096818 (d=13), A059612 (d=15), A059611 (d=17), A096819 (d=19), A096820 (d=21), A057220 (d=23), A356826 (d=29).

STATUS

approved

editing

A000043

Mersenne exponents: primes p such that 2^p - 1 is prime. Then 2^p - 1 is called a Mersenne prime.
(history; published version)

#534 by N. J. A. Sloane at Fri Jan 31 20:12:31 EST 2025

STATUS

editing

approved

#533 by N. J. A. Sloane at Fri Jan 31 20:11:59 EST 2025

LINKS

David Wasserman, <a href="/A000043/b000043.txt">Table of n, a(n) for n = 1..48</a> [Updated by N. J. A. Sloane, Feb 06 2013, Alois P. Heinz, May 01 2014, Jan 11 2015, Dec 11 2016, Ivan Panchenko, Apr 07 2018, Apr 09 2018, Benjamin Przybocki, Jan 05 2022]

STATUS

approved

editing

Discussion

Fri Jan 31

20:12

N. J. A. Sloane: Deleted a misleading and unnecessary b-file.

#532 by N. J. A. Sloane at Fri Jan 31 16:43:39 EST 2025

STATUS

editing

approved

#531 by N. J. A. Sloane at Fri Jan 31 16:43:33 EST 2025

EXTENSIONS

As of Jan 31 2025, 48 terms are known, and are shown in the DATA section. Four additional numbers are known to be in the sequence, namely 74207281, 77232917, 82589933, and 136279841, but they may not be the next terms. See the GIMP website for the latest information. - N. J. A. Sloane, Jan 31 2025

STATUS

approved

editing

A141537

An example of a simple prime-generating algorithm similar to Rowland's (A106108) that is a particular instance of a more general algorithm (see comments).
(history; published version)

#19 by N. J. A. Sloane at Fri Jan 31 13:43:03 EST 2025

STATUS

proposed

approved

A380657

Numbers whose prime factorization has more Pythagorean prime factors than non-Pythagorean prime factors (including multiplicities).
(history; published version)

#6 by N. J. A. Sloane at Fri Jan 31 13:42:02 EST 2025

STATUS

editing

approved

#5 by N. J. A. Sloane at Fri Jan 31 13:41:43 EST 2025

NAME

Numbers whose prime factorization has more non-Pythagorean prime factors than non-Pythagorean prime factors (including multiplicities).

EXAMPLE

50 appears because 2*5*5 has 2 Pythagorean prime factors and but only 1 non-Pythagorean prime factor.

STATUS

proposed

editing

Discussion

Fri Jan 31

13:42

N. J. A. Sloane: corrected defn

A380565

Irregular triangular array read by rows: (row 1) = (1); (row n+1) = inverse runlength sequence of row n, starting with 2 if r = 3k for some k, and 1 otherwise. See Comments.
(history; published version)

#4 by N. J. A. Sloane at Fri Jan 31 13:40:19 EST 2025

STATUS

proposed

approved

A380656

One of 3 limiting rows of the rectangular array A378282; this is the one that starts with 1,1,2,1,2.
(history; published version)

#8 by N. J. A. Sloane at Fri Jan 31 13:39:59 EST 2025

STATUS

proposed

approved