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A077650

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

3

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

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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