

A242739


Semiprimes having only straight digits.


1



4, 14, 74, 77, 111, 141, 177, 411, 417, 447, 471, 717, 771, 1111, 1114, 1141, 1147, 1174, 1177, 1411, 1417, 1441, 1477, 1711, 1714, 1717, 1774, 4117, 4141, 4171, 4174, 4411, 4414, 4417, 4471, 4474, 4711, 4714, 4717, 4741, 4747, 4771, 4777, 7111, 7114, 7117, 7141
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OFFSET

1,1


COMMENTS

A straight digit semiprime has only the straight digits, i.e., 1, 4 or 7.
Intersection of A001358 and A028373.  Michel Marcus, May 25 2014


LINKS

K. D. Bajpai, Table of n, a(n) for n = 1..1727


EXAMPLE

471 = 3 * 157 is semiprime and has only straight digits 4, 7 and 1. Hence it is in the sequence.
1147 = 31 * 37 is semiprime and has only straight digits 1, 1, 4 and 7. Hence it is in the sequence.


MATHEMATICA

A242739 = {}; Do[a = PrimeOmega[n]; If [a == 2 && Intersection[IntegerDigits[n], {0, 2, 3, 5, 6, 8, 9}] == {}, AppendTo[A242739, n]], {n, 8000}]; A242739


CROSSREFS

Cf. A001358, A028373, A079651, A108631, A108632.
Sequence in context: A167144 A159483 A088127 * A007282 A222900 A222485
Adjacent sequences: A242736 A242737 A242738 * A242740 A242741 A242742


KEYWORD

nonn,base


AUTHOR

K. D. Bajpai, May 21 2014


STATUS

approved



