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A118691 Semiprimes for which the digital root is also a semiprime. 0
4, 6, 9, 15, 22, 33, 49, 51, 58, 69, 85, 87, 94, 121, 123, 141, 159, 166, 177, 202, 213, 247, 249, 265, 267, 274, 301, 303, 319, 321, 339, 346, 355, 382, 391, 393, 411, 427, 445, 447, 454, 481, 501, 517, 519, 526, 535, 537, 553, 562, 573, 589, 591, 634, 679 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..55.

EXAMPLE

87 is in the sequence because (1) it is a semiprime and (2) the digital root 6 is also a semiprime.

CROSSREFS

Cf. A001358.

Sequence in context: A263106 A116589 A118688 * A087718 A033476 A183978

Adjacent sequences:  A118688 A118689 A118690 * A118692 A118693 A118694

KEYWORD

base,nonn

AUTHOR

Luc Stevens (lms022(AT)yahoo.com), May 20 2006

STATUS

approved

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Last modified April 24 22:26 EDT 2019. Contains 322446 sequences. (Running on oeis4.)