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A242868 Numbers n such that sum of the factorial of digits of n is semiprime. 3
3, 14, 15, 16, 17, 18, 22, 24, 25, 27, 28, 40, 41, 42, 50, 51, 52, 60, 61, 70, 71, 72, 80, 81, 82, 102, 104, 105, 107, 108, 112, 114, 115, 117, 118, 120, 121, 123, 125, 126, 128, 132, 140, 141, 144, 145, 146, 147, 148, 150, 151, 152, 154, 156, 157, 158, 162, 164 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
EXAMPLE
a(4) = 16: 1! + 6! = 1 + 720 = 721 = 7 * 103 which is semiprime.
a(9) = 25: 2! + 5! = 2 + 120 = 122 = 2 * 61 which is semiprime.
MAPLE
with(numtheory):A242868:= proc() local a; a:=add( i!, i = convert((n), base, 10))(n); if bigomega(a)=2 then RETURN (n); fi; end: seq(A242868 (), n=1..300);
MATHEMATICA
Select[Range[200], PrimeOmega[Total[IntegerDigits[#]!]]==2&] (* Harvey P. Dale, Jul 30 2015 *)
CROSSREFS
Sequence in context: A138959 A171653 A055435 * A070418 A178363 A294997
KEYWORD
nonn,base
AUTHOR
K. D. Bajpai, May 24 2014
STATUS
approved

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Last modified February 24 04:32 EST 2024. Contains 370288 sequences. (Running on oeis4.)