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A201018
Composite numbers whose multiplicative digital root is 5.
3
15, 35, 51, 57, 75, 115, 135, 153, 175, 315, 351, 355, 395, 511, 513, 517, 531, 535, 539, 553, 575, 579, 597, 715, 755, 759, 795, 935, 957, 975, 1115, 1135, 1157, 1175, 1315, 1351, 1355, 1359, 1395, 1513, 1517, 1535, 1539, 1557, 1575, 1593, 1715, 1751, 1755, 1795
OFFSET
1,1
COMMENTS
Complement of A201017 with respect to A034052.
LINKS
Eric Weisstein's World of Mathematics, Multiplicative Digital Root
EXAMPLE
Composite number 153 is in the sequence because 1*5*3=15, 1*5=5.
MATHEMATICA
mdr5Q[n_]:=NestWhile[Times@@IntegerDigits[#]&, n, #>9&]==5; Select[Range[1800], CompositeQ[ #] &&mdr5Q[#]&] (* Harvey P. Dale, Dec 19 2023 *)
CROSSREFS
Cf. A201017 (primes whose multiplicative digital root is 5), A034052 (numbers whose multiplicative digital root is 5).
Sequence in context: A321182 A268463 A108668 * A187400 A162280 A290781
KEYWORD
nonn,base
AUTHOR
Jaroslav Krizek, Nov 25 2011
STATUS
approved