A228019 -id:A228019 - cp's OEIS frontend

A141642 Composite numbers whose sum of digits is a prime.

12, 14, 16, 20, 21, 25, 30, 32, 34, 38, 49, 50, 52, 56, 58, 65, 70, 74, 76, 85, 92, 94, 98, 102, 104, 106, 110, 111, 115, 119, 120, 122, 124, 128, 133, 140, 142, 146, 148, 155, 160, 164, 166, 175, 182, 184, 188, 200, 201, 203, 205, 209, 210, 212, 214, 218, 221, 230, 232, 236

Offset: 1

Juri-Stepan Gerasimov, Sep 03 2008

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Cf. A046704, A163622, A228019.

Select[Range[300],CompositeQ[#]&&PrimeQ[Total[IntegerDigits[#]]]&] (* Harvey P. Dale, Feb 19 2018 *)

from sympy import isprime
def ok(n): return isprime(sum(map(int, str(n)))) and not isprime(n)
print([k for k in range(237) if ok(k)]) # Michael S. Branicky, Dec 14 2021

More terms from N. J. A. Sloane, Sep 03 2008

A228020 Composite numbers whose initial, all intermediate and final iterated digit sums are composite numbers.

Original entry on oeis.org

4, 6, 8, 9, 15, 18, 22, 24, 26, 27, 33, 35, 36, 40, 42, 44, 45, 51, 54, 60, 62, 63, 69, 72, 78, 80, 81, 87, 90, 96, 99, 105, 108, 112, 114, 116, 117, 121, 123, 125, 126, 130, 132, 134, 135, 141, 143, 144, 150, 152, 153, 159, 161, 162, 168, 170, 171, 177, 180, 186, 189, 195, 198, 202, 204, 206

Offset: 1

Derek Orr, Aug 02 2013

a(n) is congruent to 0, 4, 6 or 8 mod 9. - Robert Israel, Aug 12 2014

			78 is a term because 78, 7+8 = 15, and 1+5 = 6 are composite.

Derek Orr, Table of n, a(n) for n = 1..10000

A subset of A228019 and A104211.

filter:= proc(n) local x;
x:= n;
do
   if isprime(x) then return false fi;
   if x < 10 then return (x > 1) fi;
   x:= convert(convert(x,base,10),`+`);
od:
end proc;
select(filter,[$4..1000]); # Robert Israel, Aug 12 2014

okQ[n_] := n > 1 && !PrimeQ[n] && (n < 10 || okQ@ Total@ IntegerDigits@ n); Select[Range@168, okQ] (* Giovanni Resta, Aug 05 2013 *)
cnQ[n_]:=AllTrue[NestWhileList[Total[IntegerDigits[#]]&,n,#>9&], CompositeQ]; Select[Range[210],cnQ] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Mar 25 2016 *)

forcomposite(n=1,500,s=sumdigits(n);while(s>9&&!isprime(s)&&s!=1,s=sumdigits(s));if(!isprime(s)&&s!=1,print1(n,", "))) \\ Derek Orr, Aug 12 2014

A329522 Composite numbers whose sum of digits is not composite.

Original entry on oeis.org

10, 12, 14, 16, 20, 21, 25, 30, 32, 34, 38, 49, 50, 52, 56, 58, 65, 70, 74, 76, 85, 92, 94, 98, 100, 102, 104, 106, 110, 111, 115, 119, 120, 122, 124, 128, 133, 140, 142, 146, 148, 155, 160, 164, 166, 175, 182, 184, 188, 200, 201, 203, 205, 209, 210, 212, 214, 218, 221, 230

Offset: 1

Ali Adams, Nov 15 2019

Cf. A046704, A104213, A141642, A228019.

[k:k in [2..230]| not IsPrime(k) and (IsPrime(&+Intseq(k)) or &+Intseq(k) eq 1) ]; // Marius A. Burtea, Feb 05 2020

Select[Rest@ Complement[#, Prime@ Range@ PrimePi@ Max@ #] &@ Range@ 230, ! CompositeQ@ Total@ IntegerDigits@ # &] (* Michael De Vlieger, Nov 15 2019 *)
Select[Range[250],CompositeQ[#]&&!CompositeQ[Total[IntegerDigits[#]]]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 19 2021 *)

lista(nn) = forcomposite(c=1, nn, my(s=sumdigits(c)); if ((s==1) || isprime(s), print1(c, ", "))); \\ Michel Marcus, Nov 15 2019

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A141642 Composite numbers whose sum of digits is a prime.

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A228020 Composite numbers whose initial, all intermediate and final iterated digit sums are composite numbers.

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Maple

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A329522 Composite numbers whose sum of digits is not composite.

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Magma

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