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A279052 Semiprimes whose binary and ternary representations are prime when read in decimal. 1
295, 1189, 2515, 4399, 4897, 5137, 7045, 7261, 7999, 8065, 9019, 9637, 10579, 10951, 10963, 11035, 11233, 12679, 13315, 13603, 13849, 16279, 18295, 20065, 20467, 20497, 23089, 23419, 23551, 23983, 26359, 27007, 27301, 27787, 29647, 33127, 33253, 33763, 34189, 34411 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

K. D. Bajpai and Charles R Greathouse IV, Table of n, a(n) for n = 1..10000 (first 4075 terms from K. D. Bajpai)

EXAMPLE

295 is in the sequence because 295 = 5*59 (semiprime), 295_10 = 100100111_2 = 101221_3, and both 100100111_10 and 101221_10 are prime.

1189 is in the sequence because 1189 = 29*41 (semiprime), and both its binary representation 10010100101 and its ternary representation 1122001, if read as decimal numbers, are prime.

MATHEMATICA

Select[Range[50000], PrimeOmega[#] == 2 && PrimeQ[FromDigits[IntegerDigits[#, 2]]] && PrimeQ[FromDigits[IntegerDigits[#, 3]]] &]

PROG

(PARI) has(n, b)=isprime(fromdigits(digits(n, b), 10))

list(lim)=my(v=List(), t); forprime(p=2, lim\2, forprime(q=2, min(lim\p, p), if(has(t=p*q, 2) && has(t, 3), listput(v, t)))); Set(v) \\ Charles R Greathouse IV, Dec 05 2016

CROSSREFS

Subsequence of A001358.

Cf. A000040, A007089, A036952, A065720, A236365, A236537.

Sequence in context: A074868 A277338 A252083 * A237803 A238512 A003780

Adjacent sequences:  A279049 A279050 A279051 * A279053 A279054 A279055

KEYWORD

nonn,base

AUTHOR

K. D. Bajpai, Dec 05 2016

STATUS

approved

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Last modified November 19 18:39 EST 2019. Contains 329323 sequences. (Running on oeis4.)