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A008953 a(n) is the leading digit of the n-th triangular number, n(n+1)/2. 3
1, 3, 6, 1, 1, 2, 2, 3, 4, 5, 6, 7, 9, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 6, 6, 7, 7, 7, 8, 8, 9, 9, 9, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

R. Zumkeller, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A000030(A000217(n)). - Reinhard Zumkeller, May 12 2010]

PROG

(PARI) a(n) = digits(n*(n+1)/2)[1]; \\ Michel Marcus, Jun 20 2018

CROSSREFS

Cf. A008954. - Reinhard Zumkeller, May 12 2010

Sequence in context: A016660 A142464 A177022 * A104611 A076790 A095693

Adjacent sequences:  A008950 A008951 A008952 * A008954 A008955 A008956

KEYWORD

nonn,base

AUTHOR

N. J. A. Sloane

STATUS

approved

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Last modified October 19 15:49 EDT 2018. Contains 316365 sequences. (Running on oeis4.)