login
A308375
Digital sum of composite numbers.
0
4, 6, 8, 9, 1, 3, 5, 6, 7, 9, 2, 3, 4, 6, 7, 8, 9, 10, 3, 5, 6, 7, 8, 9, 11, 12, 4, 6, 8, 9, 10, 12, 13, 5, 6, 7, 9, 10, 11, 12, 13, 6, 8, 9, 10, 11, 12, 14, 15, 7, 9, 11, 12, 13, 14, 15, 8, 9, 10, 12, 13, 14, 15, 16, 9, 10, 11, 12, 13, 14, 15, 17, 18, 1, 3, 5
OFFSET
1,1
FORMULA
a(n) = A007953(A002808(n)).
EXAMPLE
The 6th term is 3 because the digital sum of 12 (the 6th composite number) is 3 (1+2).
MATHEMATICA
Total /@ IntegerDigits /@ Select[Range[104], CompositeQ] (* Giovanni Resta, May 28 2019 *)
PROG
(PARI) lista(nn) = forcomposite(n=1, nn, print1(sumdigits(n), ", ")); \\ Michel Marcus, May 28 2019
CROSSREFS
Cf. A002808 (composite numbers), A007953 (sum of digits).
Cf. A007605 (sum of digits of primes).
Sequence in context: A129808 A330384 A077649 * A329423 A132025 A200363
KEYWORD
nonn,easy,base
AUTHOR
Kei Ryan, May 27 2019
STATUS
approved