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A306509
a(n) is the number of divisors of the sum of digits of n.
3
1, 2, 2, 3, 2, 4, 2, 4, 3, 1, 2, 2, 3, 2, 4, 2, 4, 3, 4, 2, 2, 3, 2, 4, 2, 4, 3, 4, 2, 2, 3, 2, 4, 2, 4, 3, 4, 2, 6, 3, 2, 4, 2, 4, 3, 4, 2, 6, 2, 2, 4, 2, 4, 3, 4, 2, 6, 2, 4, 4, 2, 4, 3, 4, 2, 6, 2, 4, 4, 2, 4, 3, 4, 2, 6, 2, 4, 4, 5, 4, 3, 4, 2, 6, 2, 4, 4, 5, 2, 3, 4, 2
OFFSET
1,2
FORMULA
a(n) = A000005(A007953(n)).
a(10*n) = a(n). - Rémy Sigrist, Feb 25 2019
EXAMPLE
a(17) = A000005(A007953(17)) = A000005(8) = 4.
MATHEMATICA
Table[DivisorSigma[0, Total[IntegerDigits[n]]], {n, 120}] (* Harvey P. Dale, Aug 03 2021 *)
PROG
(PARI) a(n) = numdiv(sumdigits(n)); \\ Michel Marcus, Feb 20 2019
CROSSREFS
Sequence in context: A327536 A341946 A339915 * A083867 A076888 A357171
KEYWORD
nonn,base
AUTHOR
Ctibor O. Zizka, Feb 20 2019
STATUS
approved