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A036324 Composite numbers n such that digits of prime factors of n are either 7 or 9 or both. 3
49, 343, 553, 679, 2401, 3871, 4753, 5579, 6241, 6839, 6979, 7663, 9409, 16807, 27097, 33271, 39053, 43687, 47873, 48853, 53641, 62963, 65863, 77183, 77309, 78763, 94769, 96709, 117649, 189679, 232897, 273371, 305809, 335111, 341971 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are a product of at least two terms of A020471. - David A. Corneth, Oct 09 2020

LINKS

David A. Corneth, Table of n, a(n) for n = 1..10000 (first 100 terms from Harvey P. Dale)

Index entries for sequences related to prime factors

MATHEMATICA

Select[Range[342000], CompositeQ[#]&&SubsetQ[{7, 9}, Union[ Flatten[ IntegerDigits/@ FactorInteger[#][[All, 1]]]]]&] (* Harvey P. Dale, Aug 01 2019 *)

CROSSREFS

Cf. A020471, A036302-A036325.

Sequence in context: A036318 A020323 A036322 * A211736 A211747 A211756

Adjacent sequences:  A036321 A036322 A036323 * A036325 A036326 A036327

KEYWORD

nonn,easy,base

AUTHOR

Patrick De Geest, Dec 15 1998

EXTENSIONS

Definition clarified by Harvey P. Dale, Aug 01 2019

STATUS

approved

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Last modified January 21 05:44 EST 2021. Contains 340333 sequences. (Running on oeis4.)