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A158019 Numbers such that (n-1)/2 and 10*n-1 are both prime. 0
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 (list; graph; refs; listen; history; text; internal format)
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

Table of n, a(n) for n=1..51.

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 A256498 A054280

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

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Last modified September 19 07:24 EDT 2020. Contains 337178 sequences. (Running on oeis4.)