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

1,2

Comments

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

Links

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

Example

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

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 *)

Crossrefs

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

Sequence in context: A255787 A219340 A183997 * A233552 A176899 A361704

Adjacent sequences: A211819 A211820 A211821 * A211823 A211824 A211825

Keyword

nonn,base

Author

Jaroslav Krizek, Apr 26 2012

Status

approved