A199981 - OEIS

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A199981

Composite numbers whose multiplicative digital root is 2.

12, 21, 26, 34, 62, 112, 121, 126, 134, 143, 162, 216, 232, 261, 278, 279, 287, 297, 299, 314, 322, 341, 369, 371, 376, 396, 398, 413, 447, 469, 474, 496, 612, 621, 637, 639, 649, 666, 693, 694, 713, 728, 729, 731, 736, 744, 763, 782, 792, 872, 893, 927, 936

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

Complement of A199980 with respect to A034049.

LINKS

Table of n, a(n) for n=1..53.

EXAMPLE

Number 278 is in sequence because 2*7*8=112, 1*1*2 =2.

MATHEMATICA

t = {}; n = 0; While[Length[t] < 100, n = n + 1; If[! PrimeQ[n], s = n; While[s >= 10, s = Times @@ IntegerDigits[s]]; If[s == 2, AppendTo[t, n]]]]; t (* T. D. Noe, Nov 16 2011 *)

CROSSREFS

Cf. A199980 (primes whose multiplicative digital root is 2).

Cf. A034049 (numbers whose multiplicative digital root is 2).

Sequence in context: A349649 A327297 A371464 * A274347 A316266 A179899

Adjacent sequences: A199978 A199979 A199980 * A199982 A199983 A199984

KEYWORD

nonn,base

AUTHOR

Jaroslav Krizek, Nov 13 2011

STATUS

approved