A199983 Primes whose multiplicative digital root is 4.

41, 89, 127, 139, 193, 271, 277, 379, 383, 397, 463, 643, 677, 727, 739, 937, 1193, 1217, 1249, 1277, 1319, 1429, 1721, 1913, 1931, 1973, 2377, 2711, 3119, 3191, 3313, 3331, 3373, 3461, 3719, 3727, 3733, 3911, 3917, 4111, 4129, 4219, 6143, 7121, 7127, 7193

Offset

1,1

Comments

Complement of A199984 with respect to A034051.

Can this sequence be proved to be infinite? [Charles R Greathouse IV, Nov 13 2011]

Links

Table of n, a(n) for n=1..46.

Example

Prime 139 is in sequence because 1*3*9=27, 2*7=14, 1*4=4.

Mathematica

t = {}; n = 0; While[Length[t] < 100, n = NextPrime[n]; s = n; While[s >= 10, s = Times @@ IntegerDigits[s]]; If[s == 4, AppendTo[t, n]]]; t (* T. D. Noe, Nov 16 2011 *)

Crossrefs

Cf. A199984 (composite numbers whose multiplicative digital root is 4).

Cf. A034051 (numbers whose multiplicative digital root is 4).

Sequence in context: A087939 A242708 A282533 * A241081 A188173 A142411

Adjacent sequences: A199980 A199981 A199982 * A199984 A199985 A199986

Keyword

nonn,base

Author

Jaroslav Krizek, Nov 13 2011

Status

approved