A281252 Numbers whose septenary, octal and nonary representations are prime when read in decimal.

2, 3, 5, 43, 115, 619, 1249, 1681, 1711, 2563, 2635, 5155, 10321, 10531, 11539, 13219, 14479, 17713, 17755, 18217, 18889, 20203, 20905, 26335, 27163, 29305, 35353, 39859, 40867, 40897, 40993, 44425, 44803, 51145, 52993, 55735, 57751, 58075, 68335, 68839, 69553

Offset: 1

Author

K. D. Bajpai, Jan 22 2017

Keywords

• nonn
• base

Comments

After a(1) all the terms are odd.

After a(2) all terms are relatively prime to 42. - Charles R Greathouse IV, Jan 22 2017

Examples

			a(6) = 619 is in the sequence because 619_10 = 1543_7 = 1153_8 = 757_9; and 1543, 1153 and 757 are prime when read in decimal.
a(7) = 1249 is in the sequence because 1249_10 = 3433_7 = 2341_8 = 1637_9; and 3433, 2341 and 1637 are prime when read in decimal.
		

Links

• Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A065726, A065727, A138299, A175279, A236365.

Programs

Mathematica

Select[Range[500000], PrimeQ[FromDigits[IntegerDigits[#, 7]]] && PrimeQ[FromDigits[IntegerDigits[#, 8]]] && PrimeQ[FromDigits[IntegerDigits[#, 9]]] &]

PARI

is(n)=for(b=7,9, if(!isprime(fromdigits(digits(n,b))), return(0))); 1 \\ Charles R Greathouse IV, Jan 22 2017