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

Author

Jaroslav Krizek, Nov 13 2011

Keywords

• nonn
• base

Comments

Complement of A199984 with respect to A034051.

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

Examples

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

Crossrefs

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

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

Programs

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 *)