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A129901
For two consecutive primes p and q the difference 10*q - p is prime. The first of the pair of primes is listed.
1
3, 7, 13, 17, 19, 29, 37, 41, 67, 71, 79, 89, 101, 103, 107, 109, 149, 193, 227, 241, 269, 281, 283, 293, 307, 311, 313, 349, 389, 397, 421, 457, 479, 487, 547, 613, 617, 631, 643, 701, 709, 719, 739, 769, 829, 839, 853, 863, 877, 881, 1049, 1091, 1109, 1153
OFFSET
1,1
COMMENTS
Both can't be the same form 3n+1 or 3n+2. Since the primes alternate very frequently between 3n+1, 3n+2, 3n+1... this sequence produces a decent frequency of primes.
LINKS
EXAMPLE
For 19 and 23, 23*10 - 19 = 230-19 = 211, a prime.
MAPLE
R:= NULL: q:= 2: count:= 0:
while count < 100 do
p:= q; q:= nextprime(q);
if isprime(10*q-p) then count:= count+1; R:= R, p fi
od:
R; # Robert Israel, Jul 14 2020
MATHEMATICA
a = {}; For[n=1, n<200, n++, If[PrimeQ[10*Prime[n+1]-Prime[n]], AppendTo[a, Prime[n]]]]; a (* Stefan Steinerberger, Jun 07 2007 *)
CROSSREFS
Sequence in context: A290400 A040999 A172240 * A067073 A323579 A124273
KEYWORD
nonn
AUTHOR
J. M. Bergot, Jun 04 2007
EXTENSIONS
Corrected and extended by Stefan Steinerberger, Jun 07 2007
STATUS
approved