A004157 Sum of digits of n-th triangular number.

0, 1, 3, 6, 1, 6, 3, 10, 9, 9, 10, 12, 15, 10, 6, 3, 10, 9, 9, 10, 3, 6, 10, 15, 3, 10, 9, 18, 10, 12, 15, 19, 15, 12, 19, 9, 18, 10, 12, 15, 10, 15, 12, 19, 18, 9, 10, 12, 15, 10, 15, 12, 19, 9, 18, 10, 21, 15, 10, 15, 12, 19, 18, 9, 10, 12, 6, 19, 15, 12, 19, 18, 18, 10, 21, 15, 19, 6, 12, 10

Offset

0,3

Links

Robert Israel, Table of n, a(n) for n = 0..10000

Formula

a(n) = A007953(A000217(n)). - Robert Israel, Jun 18 2015

Maple

seq(convert(convert(n*(n+1)/2, base, 10), `+`), n=0..100); # Robert Israel, Jun 18 2015

Mathematica

Table[Plus@@IntegerDigits@(n (n + 1) / 2), {n, 0, 90}] (* Vincenzo Librandi, Jun 18 2015 *)
Total[IntegerDigits[#]]&/@Accumulate[Range[0, 100]] (* Harvey P. Dale, Mar 31 2024 *)

Prog

(Magma) [&+Intseq(n*(n+1) div 2): n in [0..80] ]; // Vincenzo Librandi, Jun 18 2015
(PARI) a(n) = sumdigits(n*(n+1)/2); \\ Michel Marcus, Jun 18 2015

Crossrefs

Cf. A000217, A007953, A062688, A145389.

Sequence in context: A134804 A145389 A055263 * A331514 A091068 A065233

Adjacent sequences: A004154 A004155 A004156 * A004158 A004159 A004160

Keyword

nonn,base

Author

N. J. A. Sloane

Status

approved