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URL: https://oeis.org/A387093

⇱ A387093 - OEIS


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A387093
Composite numbers that contain only prime digits and whose prime factors contain only prime digits.
2
25, 27, 32, 35, 72, 75, 222, 225, 252, 322, 333, 375, 525, 552, 555, 575, 735, 777, 2352, 2553, 2555, 2775, 3357, 3375, 3552, 3577, 5222, 5352, 5575, 7252, 7322, 23253, 23373, 23532, 23535, 23552, 25275, 25725, 25737, 27232, 27252, 27375, 32352, 32375
OFFSET
1,1
LINKS
Scott R. Shannon, Table of n, a(n) for n = 1..2298 (all terms < 10^12).
EXAMPLE
25725 is a term as 25725 = 3 * 5^2 * 7^3, and both the number and its prime factors only contain prime digits.
MATHEMATICA
Select[Select[Range[33000], CompositeQ], And[AllTrue[Union@ IntegerDigits[#], PrimeQ], AllTrue[Union@ Flatten@ Map[IntegerDigits, FactorInteger[#][[All, 1]] ], PrimeQ]] &] (* Michael De Vlieger, Aug 16 2025 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Scott R. Shannon and Ursula Ponting, Aug 16 2025
STATUS
approved