A277216 Product of decimal digits of sum of divisors of n.

1, 3, 4, 7, 6, 2, 8, 5, 3, 8, 2, 16, 4, 8, 8, 3, 8, 27, 0, 8, 6, 18, 8, 0, 3, 8, 0, 30, 0, 14, 6, 18, 32, 20, 32, 9, 24, 0, 30, 0, 8, 54, 16, 32, 56, 14, 32, 8, 35, 27, 14, 72, 20, 0, 14, 0, 0, 0, 0, 48, 12, 54, 0, 14, 32, 16, 48, 12, 54, 16, 14, 45, 28, 4, 8

Offset

1,2

Comments

Conjecture: a(n) = n only for numbers 1 and 210; sigma(210) = 576; a(210) = 5*7*6 = 210.

Links

Jaroslav Krizek, Table of n, a(n) for n = 1..1000

Formula

a(n) = A007954(A000203(n)).

Example

a(12) = 16 because sigma(12) = 28; 2*8 = 16.

Maple

seq( convert(convert(numtheory:-sigma(n), base, 10), `*`), n=1..100); # Robert Israel, Oct 06 2016

Mathematica

Table[Times @@ IntegerDigits@ DivisorSigma[1, n], {n, 75}] (* Michael De Vlieger, Oct 06 2016 *)

Prog

(Magma) [&*Intseq(SumOfDivisors(n)): n in [1..100000]]
(PARI) a(n) = d = digits(sigma(n)); prod(k=1, #d, d[k]); \\ Michel Marcus, Oct 05 2016

Crossrefs

Cf. A067342 (sum of decimal digits of sigma(n)).

Cf. A000203, A007954, A277217.

Sequence in context: A244669 A316570 A105853 * A323394 A348977 A017665

Adjacent sequences: A277213 A277214 A277215 * A277217 A277218 A277219

Keyword

nonn,base

Author

Jaroslav Krizek, Oct 05 2016

Status

approved