

A157137


Odd composite numbers k such that k and prime(k) have the same number of prime digits.


0



15, 33, 39, 45, 75, 81, 85, 93, 115, 117, 123, 133, 141, 145, 169, 183, 185, 187, 195, 205, 207, 209, 213, 231, 243, 247, 259, 261, 273, 275, 287, 289, 295, 299, 301, 315, 321, 325, 333, 335, 339, 343, 363, 365, 385, 387, 391, 395, 427, 477, 505, 517, 527
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OFFSET

1,1


COMMENTS

Prime digits are 2, 3, 5 or 7.


LINKS

Table of n, a(n) for n=1..53.


EXAMPLE

15 is a term: prime(15)=47, and 15 and 47 each have one prime digit.
33 is a term: prime(33)=137, and 33 and 137 each have two prime digits.
39 is a term: prime(39)=167, and 39 and 167 each have two prime digits.


CROSSREFS

Cf. A000027, A000040, A155548.
Sequence in context: A089967 A064900 A277254 * A141230 A140608 A085371
Adjacent sequences: A157134 A157135 A157136 * A157138 A157139 A157140


KEYWORD

nonn,base


AUTHOR

JuriStepan Gerasimov, Feb 24 2009


EXTENSIONS

Corrected by R. J. Mathar, Feb 26 2009
Edited by Jon E. Schoenfield, Apr 18 2021


STATUS

approved



