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A086080
Number of 9's in decimal expansion of triangular number n(n+1)/2.
11
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0
OFFSET
0,45
LINKS
Antti Karttunen, Table of n, a(n) for n = 0..65537 [shifted by Georg Fischer, Apr 28 2021]
MATHEMATICA
DigitCount[Accumulate[Range[0, 100]], 10, 9] (* Paolo Xausa, May 05 2024 *)
PROG
(PARI) A086080(n) = length(select(d -> (9==d), digits(binomial(n+1, 2)))); \\ Antti Karttunen, Sep 27 2018; corrected by Georg Fischer Apr 28 2021
CROSSREFS
Cf. A000217.
Cf. 0's A086071, 1's A086072, 2's A086073, 3's A086074, 4's A086075, 5's A086076, 6's A086077, 7's A086078, 8's A086079.
Sequence in context: A071164 A027345 A328959 * A369054 A281477 A070139
KEYWORD
base,nonn
AUTHOR
Jason Earls, Jul 08 2003
EXTENSIONS
Zero at the beginning inserted by Antti Karttunen, Sep 27 2018
Zero at the beginning removed by Georg Fischer, Apr 28 2021
STATUS
approved