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A129287 Number of Harshad numbers between 10^n and 10^n + 100. 1
29, 30, 31, 29, 30, 28, 29, 30, 30, 29, 28, 28, 29, 30, 30, 29, 29, 28, 30, 30, 31, 29, 29, 28, 29, 30, 30, 29, 28, 28, 29, 30, 31, 29, 29, 28, 30, 30, 30, 29, 29, 28, 29, 30, 30, 29, 28, 28, 30, 30, 31, 29, 29, 28, 29, 30, 30, 29, 29, 28, 29, 30, 30, 29, 29, 28, 30, 30, 31 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,1

COMMENTS

Will every term be between 28 and 31 inclusive?

REFERENCES

Jason Earls, Red Zen, Lulu Press, NY, 2006, pp. 145-146. ISBN: 978-1-4303-2017-3.

LINKS

Amiram Eldar, Table of n, a(n) for n = 3..10000

EXAMPLE

There are exactly 29 Harshad numbers between 1000 and 1100, so the first term is 29.

MATHEMATICA

a[n_] := Count[Range[10^n, 10^n + 100], _?(Divisible[#, Plus @@ IntegerDigits[#]] &)]; Array[a, 70, 3] (* Amiram Eldar, Jan 27 2021 *)

CROSSREFS

Cf. A005349.

Sequence in context: A210267 A210309 A165850 * A007642 A295749 A022399

Adjacent sequences:  A129284 A129285 A129286 * A129288 A129289 A129290

KEYWORD

nonn,base

AUTHOR

Jason Earls, May 26 2007

STATUS

approved

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Last modified July 31 02:33 EDT 2021. Contains 346367 sequences. (Running on oeis4.)