A211822 Nonprime numbers with all divisors with additive digital root of 1.

1, 361, 703, 1369, 1387, 2071, 2413, 2701, 3097, 3439, 3781, 4033, 4699, 5149, 5329, 5833, 6031, 6697, 6859, 7201, 7363, 7543, 7957, 8227, 9253, 9271, 9937, 10027, 10279, 10963, 11359, 11647, 11881, 11899, 11989, 13213, 13357

Offset: 1

Author

Jaroslav Krizek, Apr 26 2012

Keywords

• nonn
• base

Comments

Complement of A061237 (prime numbers == 1 (mod 9)) with respect to A211821.

Examples

			Number 6859 with divisors 1, 19, 361, 6859 is in sequence because all divisors have additive digital root of 1.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A211821, A024906, A061237, A017173, A211823.

Programs

Maple

filter:= n -> not isprime(n) and numtheory:-factorset(n) mod 9 = {1}:
filter(1):= true:
select(filter, [seq(i,i=1..20000,9)]); # Robert Israel, May 10 2020

Mathematica

(* First run the program for A211821 *) Select[A211821, Not[PrimeQ[#]] &] (* Alonso del Arte, May 02 2012 *)