A228455 -id:A228455

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A230668

Smallest of 5 consecutive odd numbers that are primes or pseudoprime (base 2).

+10
3

280743771536011781, 666787209284980781, 1386744766793550161, 6558237049521329741, 11646802313400102461

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

It is conjectured that all numbers in this sequence ends in 1.

All terms known so far are of the form A228455(n) - 4. - M. F. Hasler, Dec 08 2016

LINKS

Table of n, a(n) for n=1..5.

EXAMPLE

280743771536011781 is in sequence because 280743771536011781, 280743771536011783, 280743771536011785, 280743771536011787, 280743771536011789 is a set of 5 consecutive odd number where 280743771536011785 is pseudoprime base 2 and others are prime.

CROSSREFS

Cf. A001567, A228455.

KEYWORD

nonn,hard,more

AUTHOR

Shyam Sunder Gupta, Oct 27 2013

EXTENSIONS

Definition reworded by M. F. Hasler, Dec 08 2016

STATUS

approved

A230667

Smallest starting number for n consecutive odd numbers that are primes or pseudoprime (base 2).

+10
2

3, 3, 3, 641, 280743771536011781

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

It is conjectured that the sequence is full, that is, a(6) does not exist.

LINKS

Table of n, a(n) for n=1..5.

EXAMPLE

First and smallest occurrence of n, n >= 1, consecutive odd numbers that are primes or pseudoprimes (base 2):

a(1) = 3: (3) ;

a(2) = 3: (3, 5) ;

a(3) = 3: (3, 5, 7);

a(4) = 641: (641, 643, 645, 647); (645 is pseudoprime base 2 and others are prime);

a(5) = 280743771536011781: (280743771536011781, 280743771536011783, 280743771536011785, 280743771536011787, 280743771536011789); (280743771536011785 is pseudoprime base 2 and others are prime).