A316570 Multiplicative digital root of sigma(n).

1, 3, 4, 7, 6, 2, 8, 5, 3, 8, 2, 6, 4, 8, 8, 3, 8, 4, 0, 8, 6, 8, 8, 0, 3, 8, 0, 0, 0, 4, 6, 8, 6, 0, 6, 9, 8, 0, 0, 0, 8, 0, 6, 6, 0, 4, 6, 8, 5, 4, 4, 4, 0, 0, 4, 0, 0, 0, 0, 6, 2, 0, 0, 4, 6, 6, 6, 2, 0, 6, 4, 0, 6, 4, 8, 0, 0, 6, 0, 6, 2, 2, 6, 6, 0, 6, 0

Offset

1,2

Comments

Multiplicative digital root of A000203(n).

Links

Table of n, a(n) for n=1..87.

Formula

a(n) = A031347(A000203(n)).

Example

For n = 12: sigma(12) = 28; a(n) = 6 because 2 * 8 = 16; 1 * 6 = 6.

Maple

m:= n-> `if`(n<10, n, m(mul(d, d=convert(n, base, 10)))):
a:= n-> m(numtheory[sigma](n)):
seq(a(n), n=1..100);  # Alois P. Heinz, Jul 21 2018

Prog

(PARI) a031347(n) = while(n>9, n=prod(i=1, #n=digits(n), n[i])); n;
a(n) = a031347(sigma(n)); \\ Michel Marcus, Jul 07 2018

Crossrefs

Cf. A000203, A031347.

Cf. A190998 (additive digital root of sigma(n)).

Sequence in context: A134688 A077650 A244669 * A105853 A277216 A323394

Adjacent sequences: A316567 A316568 A316569 * A316571 A316572 A316573

Keyword

nonn,base

Author

Jaroslav Krizek, Jul 07 2018

Status

approved