A199978 - OEIS

A199978

Nonprime numbers whose multiplicative digital root is 0.

10, 20, 25, 30, 40, 45, 50, 52, 54, 55, 56, 58, 60, 65, 69, 70, 78, 80, 85, 87, 90, 95, 96, 100, 102, 104, 105, 106, 108, 110, 120, 125, 130, 140, 145, 150, 152, 154, 155, 156, 158, 159, 160, 165, 169, 170, 178, 180, 185, 187, 190, 195, 196, 200, 201, 202

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OFFSET

1,1

COMMENTS

Complement of A199977 with respect to A034048.

LINKS

Table of n, a(n) for n=1..56.

EXAMPLE

Number 58 is in sequence because 5*8 = 40, 4*0 = 0.

MATHEMATICA

digRoot[n_] := Module[{k = n}, While[k > 9, k = Times @@ IntegerDigits[k]]; k]; Select[Range[300], ! PrimeQ[#] && digRoot[#] == 0 &] (* T. D. Noe, Nov 23 2011 *)

CROSSREFS

Cf. A199977 (primes whose multiplicative digital root is 0).

Sequence in context: A144140 A361337 A034048 * A342142 A179819 A320522

Adjacent sequences: A199975 A199976 A199977 * A199979 A199980 A199981

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Nov 13 2011

STATUS

approved