A372281 - OEIS

A372281

Numbers written in base of triangular numbers where the trailing digits are made as high as possible.

1, 2, 3, 4, 5, 6, 7, 8, 9, 17, 18, 19, 27, 28, 29, 37, 38, 39, 47, 48, 49, 57, 58, 59, 67, 68, 69, 77, 78, 79, 87, 88, 89, 97, 98, 99, 187, 188, 189, 197, 198, 199, 287, 288, 289, 297, 298, 299, 387, 388, 389, 397, 398, 399, 487, 488, 489, 497, 498, 499, 587

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OFFSET

1,2

COMMENTS

This sequence differs from A000462 whose leading digits are made as high as possible.

LINKS

Table of n, a(n) for n=1..61.

EXAMPLE

The digits (from right to left) have values 1, 3, 6, 10, etc. (A000217), hence a(61) = 587 because 61 = 5*6 + 8*3 + 7*1.

MATHEMATICA

A000217[n_]:=n(n+1)/2; a[n_]:=Module[{s=0}, num=n; digits={}; s=Ceiling[Root[9(#1^3+3#1^2+2#1)-6num &, 1]]; While[s>0, AppendTo[digits, d=Ceiling[(num-9(s-1)^2)/A000217[s]]]; num-=d*A000217[s]; s--]; FromDigits[digits]]; Array[a, 61]

CROSSREFS

Cf. A000217, A000462.

9*A000292(n) gives the number of terms with at most n digits.

Sequence in context: A108971 A179977 A326298 * A124359 A124366 A289868

Adjacent sequences: A372278 A372279 A372280 * A372282 A372283 A372284

KEYWORD

nonn,base,easy

AUTHOR

Stefano Spezia, Apr 25 2024

STATUS

approved