A118693 Semiprimes which are divisible by the sum of their digits.
4, 6, 9, 10, 21, 111, 133, 201, 209, 247, 407, 481, 511, 629, 803, 1011, 1101, 1141, 1387, 1417, 1651, 1679, 1853, 2119, 2159, 2353, 2771, 3031, 3077, 3097, 3383, 3439, 3523, 3749, 3781, 4577, 4607, 5149, 5161, 5219, 5833, 6331, 6443, 7033, 7361, 7501
Offset: 1
Examples
133 is in the sequence because it is a semiprime and it is divisible by the sum of its digits, 1+3+3 = 7.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
-
Mathematica
spQ[n_] := Plus @@ Last /@ FactorInteger@n == 2; Select[Range@7542, spQ@# && IntegerQ[ #/Plus @@ IntegerDigits@# ] &] (* Robert G. Wilson v, Jun 10 2006 *)
Extensions
More terms from Robert G. Wilson v, Jun 10 2006