A069833 - OEIS

%I #17 Oct 14 2019 07:06:48

%S 7,19,37,41,91,199,209,239,311,539,587,661,749,923,931,941,967,1009,

%T 1079,1139,1997,2717,2959,3971,3979,4559,4993,4999,5393,5629,5651,

%U 6401,6739,6911,8213,8491,8939,9109,9397,9607,9679,9829,11089,11227,13943

%N Prefixing, suffixing or inserting a 9 in the number anywhere gives a prime.

%H Giovanni Resta, <a href="/A069833/b069833.txt">Table of n, a(n) for n = 1..2128</a> (terms < 10^13, first 1175 terms from Chai Wah Wu)

%o (PARI) is(n,L=logint(n+!n,10)+1,d,P)={!for(k=0,L,isprime((d=divrem(n,P=10^(L-k)))[2]+(10*d[1]+9)*P)||return)} \\ _M. F. Hasler_, May 10 2018

%Y Cf. A215421 (subsequence of primes).

%Y Cf. A068679 (1 is prefixed, appended or inserted anywhere), A069246 (primes among these), A068673 (1 is prefixed, or appended).

%Y Cf. A158594 (3 is prefixed, appended or inserted anywhere), A215419 (primes among these).

%Y Cf. A069832 (7 is prefixed, appended or inserted anywhere), A215420 (primes among these), A068677 (7 is prefixed or appended).

%Y Cf. A158232 (13 is prefixed or appended).

%Y Cf. A164329 (0 is inserted), A216169 (subset of composite terms), A215417 (subset of primes), A159236 (0 is inserted between all digits).

%K nonn,base

%O 1,1

%A _Amarnath Murthy_, Apr 14 2002

%E More terms from _Vladeta Jovovic_, Apr 16 2002

%E Corrected offset by _Chai Wah Wu_, Oct 10 2019