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A133296

Smallest number whose sum of digits is 2n.

0, 2, 4, 6, 8, 19, 39, 59, 79, 99, 299, 499, 699, 899, 1999, 3999, 5999, 7999, 9999, 29999, 49999, 69999, 89999, 199999, 399999, 599999, 799999, 999999, 2999999, 4999999, 6999999, 8999999, 19999999, 39999999, 59999999, 79999999, 99999999, 299999999, 499999999

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OFFSET

0,2

LINKS

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Index entries for linear recurrences with constant coefficients, signature (1,0,0,0,0,0,0,0,100,-100).

FORMULA

From Alois P. Heinz, Mar 12 2025: (Start)

G.f.: x*(20*x^8+20*x^7+20*x^6+20*x^5+11*x^4+2*x^3+2*x^2+2*x+2)/((x-1)*(100*x^9-1)).

a(n) = A051885(2*n). (End)

MAPLE

a:= n-> parse(cat(irem(2*n, 9, 'r'), 9$r)):