A131668 -id:A131668 - cp's OEIS frontend

A131766 a(n) = A131668(n) - (2*n+1).

0, 0, 0, 0, 0, 18, 36, 54, 72, 180, 378, 576, 774, 972, 2970, 4968, 6966, 8964, 19962, 39960, 59958, 79956, 99954, 299952, 499950, 699948, 899946, 1999944, 3999942, 5999940, 7999938, 9999936, 29999934, 49999932, 69999930, 89999928, 199999926, 399999924, 599999922

Offset: 0

Paul Curtz, Oct 04 2007

Digital sums: 9*A002266.

Index entries for linear recurrences with constant coefficients, signature (2,-1,0,0,0,0,0,0,100,-200,100).

Cf. A002266, A131668, A131871.

a(30) corrected and more terms from Georg Fischer, Jul 30 2025

A133296 Smallest number whose sum of digits is 2n.

Original entry on oeis.org

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

Offset: 0

Paul Curtz, Oct 17 2007

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

Bisection of A051885 (even part).

Cf. A131668.

a:= n-> parse(cat(irem(2*n, 9, 'r'), 9$r)):
seq(a(n), n=0..38);  # Alois P. Heinz, Mar 12 2025

a[n_] := (Mod[2n, 9] + 1)*10^Floor[2n/9] - 1; Table[a[n], {n, 0,38}] (* James C. McMahon, Mar 13 2025 *)

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)

cp's OEIS Frontend

A131766 a(n) = A131668(n) - (2*n+1).

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A133296 Smallest number whose sum of digits is 2n.

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