login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A258661 Positive integers m such that none of the four consecutive numbers m, m+1, m+2, m+3 can be written as p^2 + q with p and q both prime. 1
1, 2, 1009, 3598, 4354, 9214, 11662, 15051, 15052, 15873, 15874, 19042, 21772, 22497, 22498, 24334, 26242, 46654, 60514, 76173, 76174, 93634, 97341, 97342, 108898, 112893, 112894, 121101, 121102, 133954, 152098, 156813, 156814, 166462, 171393, 171394, 181473, 181474, 202498, 213441, 213442, 224674, 236193, 236194, 254013, 254014, 266253, 266254, 272482, 278781 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Conjecture: Any term not among 1, 2, 1009, 15051, 15052, 21772 has the form 36*k^2-2 or the form 36*k^2-3, where k is a positive integer.

Note that this conjecture implies the conjecture in A258168 since neither 36*k^2-2 nor 36*k^2-3 can be a multiple of 5.

For more comments, see the linked message to Number Theory Mailing List.

LINKS

Zhi-Wei Sun, Table of n, a(n) for n = 1..500

Zhi-Wei Sun, Re: A new conjecture involving p^2+q, a message to Number Theory Mailing List, May 30, 2015.

EXAMPLE

a(1) = 1 since none of 1,2,3,4 has the form p^2+q with p and q both prime.

a(2) = 2 since none of 2,3,4,5 has the form p^2+q with p and q both prime.

MATHEMATICA

n=0; Do[Do[If[PrimeQ[m+r-Prime[k]^2], Goto[aa]], {r, 0, 3}, {k, 1, PrimePi[Sqrt[m+r]]}]; n=n+1; Print[n, " ", m]; Label[aa]; Continue, {m, 1, 278781}]

CROSSREFS

Cf. A000040, A258139, A258140, A258141, A258168.

Sequence in context: A190579 A271527 A214543 * A024033 A255569 A004897

Adjacent sequences:  A258658 A258659 A258660 * A258662 A258663 A258664

KEYWORD

nonn

AUTHOR

Zhi-Wei Sun, Jun 06 2015

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 23 14:53 EDT 2018. Contains 316528 sequences. (Running on oeis4.)