A158019 Numbers such that (n-1)/2 and 10*n-1 are both prime.

11, 15, 23, 27, 35, 39, 83, 107, 123, 143, 167, 179, 195, 203, 207, 227, 255, 275, 279, 347, 399, 423, 455, 479, 567, 587, 623, 627, 695, 707, 735, 759, 767, 779, 795, 839, 843, 863, 867, 935, 975, 983, 1007, 1043, 1095, 1115, 1155, 1215, 1227, 1283, 1323

Offset

1,1

Comments

Relating the two prime types:

(p-1)/2,(p-1)/4,(p-1)/6,(p-1)/8,(p-1)/10,(p-1)/12...

and

2*p-1,4*p-1,6*p-1,8*p-1,10*p-1...

where both contain 11,23 subsequence.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Maple

filter:= proc(n) isprime((n-1)/2) and isprime(10*n-1) end proc:
select(filter, [seq(i, i=3..10000, 4)]); # Robert Israel, Dec 12 2024

Mathematica

Flatten[Table[If[PrimeQ[(n - 1)/2] && PrimeQ[10*n - 1], n, {}], {n, 1, 10000}]]
Select[Range[1, 1500, 2], PrimeQ[(#-1)/2]&&PrimeQ[10#-1]&] (* Harvey P. Dale, Mar 10 2013 *)

Crossrefs

Sequence in context: A045564 A285271 A087142 * A228205 A343416 A256498

Adjacent sequences: A158016 A158017 A158018 * A158020 A158021 A158022

Keyword

nonn

Author

Roger L. Bagula and Gary W. Adamson, Mar 11 2009, Mar 20 2009

Status

approved