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A196000 Numbers k such that 90*k + 19 is prime. 21

%I

%S 0,1,2,4,8,9,10,11,14,16,17,22,23,24,25,28,30,34,35,36,39,41,43,46,48,

%T 50,53,55,56,60,63,64,65,69,74,77,78,79,80,81,83,85,86,91,93,98,99,

%U 101,102,107,108,109,111,112,115,116

%N Numbers k such that 90*k + 19 is prime.

%C A142322 is a digital root 1 and last digit 9 preserving sequence.

%H Ivan Neretin, <a href="/A196000/b196000.txt">Table of n, a(n) for n = 1..10000</a>

%F a(n) = (A142322(n) - 19)/90.

%p A142322 := proc(n)

%p option remember;

%p if n = 1 then

%p 19 ;

%p else

%p a := nextprime(procname(n-1)) ;

%p while (a mod 45) <> 19 do

%p a := nextprime(a) ;

%p end do;

%p return a;

%p end if;

%p end proc:

%p A196000 := proc(n)

%p (A142322(n)-19)/90 ;

%p end proc:

%p seq(A196000(n),n=1..80) ; # _R. J. Mathar_, Oct 31 2011

%t Select[Range[0, 120], PrimeQ[90 # + 19] &] (* _Ivan Neretin_, Apr 27 2017 *)

%o (PARI) is(n)=isprime(90*n+19) \\ _Charles R Greathouse IV_, Apr 25 2016

%Y Cf. A195953, A181732, A198382.

%K nonn,easy

%O 1,3

%A _J. W. Helkenberg_, Oct 27 2011

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Last modified August 8 02:41 EDT 2020. Contains 336290 sequences. (Running on oeis4.)