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A110604 Numbers n whose base 6 representations, interpreted as base 10 integers, are semiprimes. 6
4, 6, 10, 11, 13, 14, 17, 21, 22, 23, 31, 35, 43, 47, 49, 50, 51, 57, 58, 61, 62, 63, 65, 71, 73, 74, 75, 77, 81, 82, 83, 85, 95, 105, 106, 109, 110, 111, 113, 118, 121, 123, 130, 131, 133, 143, 147, 151, 153, 155, 158, 173, 175, 177, 178, 181, 182, 185, 187, 190, 191 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A108873 is the equivalent using base 3. A110602 is the equivalent using base 4. A110603 is the equivalent using base 5. A110605 is the equivalent using base 7. A110606 is the equivalent using base 8. A110607 is the equivalent using base 9.

LINKS

Table of n, a(n) for n=1..61.

EXAMPLE

a(1) = 4 because 4 (base 6) = 4 and 4 (base 10) = 2 * 2, a semiprime (A001358).

a(2) = 6 because 6 (base 6) = 10 and 10 (base 10) = 2 * 5.

a(3) = 10 because 10 (base 6) = 14 and 14 (base 10) = 2 * 7.

a(4) = 11 because 11 (base 6) = 15 and 15 (base 10) = 3 * 5.

a(5) = 13 because 13 (base 6) = 21 and 21 (base 10) = 3 * 7.

MATHEMATICA

Select[Range[191], Plus @@ Last /@ FactorInteger[FromDigits[IntegerDigits[ #, 6]]] == 2 &] (* Ray Chandler, Aug 05 2005 *)

Select[Range[200], PrimeOmega[FromDigits[IntegerDigits[#, 6]]]==2&] (* Harvey P. Dale, Oct 02 2011 *)

CROSSREFS

Cf. A001358, A007092, A108873, A110602, A110603, A110605, A110606, A110607.

Sequence in context: A171615 A141780 A185002 * A109270 A187331 A184923

Adjacent sequences:  A110601 A110602 A110603 * A110605 A110606 A110607

KEYWORD

base,easy,nonn

AUTHOR

Jonathan Vos Post, Jul 30 2005

EXTENSIONS

Corrected and extended by Ray Chandler, Aug 05 2005

STATUS

approved

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Last modified July 26 08:42 EDT 2021. Contains 346294 sequences. (Running on oeis4.)