A110606 Numbers n whose base 8 representations, interpreted as base 10 integers, are semiprimes.

4, 6, 8, 12, 13, 17, 18, 21, 22, 27, 28, 29, 38, 41, 45, 47, 50, 53, 60, 63, 70, 73, 77, 81, 82, 83, 91, 92, 97, 98, 99, 101, 102, 109, 113, 118, 127, 129, 130, 131, 133, 134, 139, 140, 141, 143, 145, 150, 157, 159, 167, 171, 172, 178, 181, 183, 188, 193, 194, 195

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. A110604 is the equivalent using base 6. A110605 is the equivalent using base 7. A110607 is the equivalent using base 9.

Links

Table of n, a(n) for n=1..60.

Example

a(1) = 4 because 4 (base 8) = 4 (base 10) = 2 * 2, a semiprime (A001358).
a(2) = 6 because 6 (base 8) = 6 (base 10) = 2 * 3.
a(3) = 8 because 8 (base 8) = 10 and 10 (base 10) = 2 * 5.
a(4) = 12 because 12 (base 8) = 14 and 14 (base 10) = 2 * 7.
a(5) = 13 because 13 (base 8) = 15 and 15 (base 10) = 3 * 5.

Mathematica

Select[Range[195], Plus @@ Last /@ FactorInteger[FromDigits[IntegerDigits[ #, 8]]] == 2 &] (* Ray Chandler, Aug 05 2005 *)

Crossrefs

Cf. A001358, A007094, A108873, A110602, A110603, A110604, A110605, A110607.

Sequence in context: A274790 A179852 A281020 * A346124 A241124 A117247

Adjacent sequences: A110603 A110604 A110605 * A110607 A110608 A110609

Keyword

base,easy,nonn

Author

Jonathan Vos Post, Jul 30 2005

Extensions

Extended by Ray Chandler, Aug 05 2005

Status

approved