A244248 - OEIS

A244248

Semiprimes whose binary representation, read in decimal, is prime.

185, 247, 253, 295, 329, 355, 453, 471, 533, 565, 583, 671, 689, 703, 755, 781, 785, 815, 841, 989, 1037, 1099, 1121, 1159, 1189, 1207, 1219, 1329, 1403, 1441, 1473, 1541, 1555, 1643, 1661, 1703, 1751, 1793, 1797, 1819, 1821, 1853, 1921, 1941, 1957, 2123, 2189

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OFFSET

1,1

COMMENTS

Semiprimes in A036952.

Intersection of A001358 and A036952.

LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..10000

EXAMPLE

a(1) = 185 = 5 * 37 which is semiprime. Binary representation of 185 = 10111001 which is prime.

a(2) = 247 = 13 * 19 which is semiprime. Binary representation of 247 = 11110111 which is prime.

MAPLE

with(numtheory):A244248 := proc() local a; a:=convert(n, binary); if bigomega(n)=2 and isprime(a) then RETURN (n) ; fi; end: seq(A244248 (), n=1..5000);

MATHEMATICA

A244248={}; Do[If[PrimeOmega[n]==2&&PrimeQ[FromDigits[IntegerDigits[n, 2]]], AppendTo[A244248, n]], {n, 5000}]; A244248

CROSSREFS

Cf. A000040, A001358, A036952, A242677.

Sequence in context: A362096 A157297 A156059 * A129311 A252272 A247529

Adjacent sequences: A244245 A244246 A244247 * A244249 A244250 A244251

KEYWORD

nonn,base

AUTHOR

K. D. Bajpai, Jun 23 2014

STATUS

approved