A201018 Composite numbers whose multiplicative digital root is 5.

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

Harvey P. Dale, Table of n, a(n) for n = 1..1000

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

Adjacent sequences: A201015 A201016 A201017 * A201019 A201020 A201021

Keyword

nonn,base

Author

Jaroslav Krizek, Nov 25 2011

Status

approved