A281252 - OEIS

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

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OFFSET

1,1

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

LINKS

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

EXAMPLE

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.

MATHEMATICA

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

PROG

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

CROSSREFS

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

Sequence in context: A042469 A107990 A117460 * A208223 A136371 A060380

Adjacent sequences: A281249 A281250 A281251 * A281253 A281254 A281255

KEYWORD

nonn,base

AUTHOR

K. D. Bajpai, Jan 22 2017

STATUS

approved