A077650 Initial decimal digit of sigma(n), the sum of divisors of n.

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

Offset

1,2

Links

Antti Karttunen, Table of n, a(n) for n = 1..10000

Index entries for sequences related to sigma(n)

Formula

a(n) = A000030(A000203(n)).

Mathematica

Table[First[IntegerDigits[DivisorSigma[1, w]]], {w, 1, 128}]

Prog

(PARI) a(n) = digits(sigma(n))[1]; \\ Michel Marcus, Nov 18 2017

Crossrefs

Cf. A000030, A000203, A067342.

Sequence in context: A010613 A299693 A134688 * A244669 A316570 A105853

Adjacent sequences: A077647 A077648 A077649 * A077651 A077652 A077653

Keyword

base,nonn

Author

Labos Elemer, Nov 19 2002

Status

approved