A211822 - OEIS

%I #10 May 10 2020 19:34:21

%S 1,361,703,1369,1387,2071,2413,2701,3097,3439,3781,4033,4699,5149,

%T 5329,5833,6031,6697,6859,7201,7363,7543,7957,8227,9253,9271,9937,

%U 10027,10279,10963,11359,11647,11881,11899,11989,13213,13357

%N Nonprime numbers with all divisors with additive digital root of 1.

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

%H Robert Israel, <a href="/A211822/b211822.txt">Table of n, a(n) for n = 1..10000</a>

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

%p filter:= n -> not isprime(n) and numtheory:-factorset(n) mod 9 = {1}:

%p filter(1):= true:

%p select(filter, [seq(i,i=1..20000,9)]); # _Robert Israel_, May 10 2020

%t (* First run the program for A211821 *) Select[A211821, Not[PrimeQ[#]] &] (* _Alonso del Arte_, May 02 2012 *)

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

%K nonn,base

%O 1,2

%A _Jaroslav Krizek_, Apr 26 2012