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 A346535 Numbers obtained by adding the first k repdigits that consist of the same digit, for some number k. 2
 1, 2, 3, 4, 5, 6, 7, 8, 9, 12, 24, 36, 48, 60, 72, 84, 96, 108, 123, 246, 369, 492, 615, 738, 861, 984, 1107, 1234, 2468, 3702, 4936, 6170, 7404, 8638, 9872, 11106, 12345, 24690, 37035, 49380, 61725, 74070, 86415, 98760, 111105, 123456, 246912, 370368, 493824 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 LINKS Index entries for linear recurrences with constant coefficients, signature (0,0,0,0,0,0,0,0,12,0,0,0,0,0,0,0,0,-21,0,0,0,0,0,0,0,0,10). FORMULA a(n) = d*A014824(m) where d = (n-1) mod 9 + 1 and m = ceiling(n/9). - Jon E. Schoenfield, Jul 22 2021 G.f.: x*(1 + 2*x + 3*x^2 + 4*x^3 + 5*x^4 + 6*x^5 + 7*x^6 + 8*x^7 + 9*x^8)/((1 - x^9)^2*(1 - 10*x^9)). - Stefano Spezia, Jul 26 2021 EXAMPLE a(1) = 1, a(2) = 2, a(3) = 3, ... a(9) = 9; a(10) = 1 + 11 = 12, a(11) = 2 + 22 = 24, a(12) = 3 + 33 = 36, ... a(18) = 9 + 99 = 108; a(19) = 1 + 11 + 111 = 123, a(20) = 2 + 22 + 222 = 246, a(21) = 3 + 33 + 333 = 369, ... a(27) = 9 + 99 + 999 = 1107; ... MATHEMATICA Table[m*(10^(1+k)-10-9*k)/81, {k, 6}, {m, 9}]//Flatten (* Stefano Spezia, Aug 17 2021 *) PROG (Python 3) def sumRepUnits(n): # A014824 return ((10**n-1)*10 - 9*n)//81 def a(n): # A346535 d = 1 + (n-1)%9 m = 1 + (n-1)//9 return d*sumRepUnits(m) for n in range(1, 1000): print(n, a(n)) CROSSREFS Cf. A010785, A014824. Sequence in context: A259236 A138141 A228017 * A227224 A236750 A001102 Adjacent sequences: A346532 A346533 A346534 * A346536 A346537 A346538 KEYWORD nonn,base,easy AUTHOR Jwalin Bhatt, Jul 22 2021 STATUS approved

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Last modified March 20 05:00 EDT 2023. Contains 361358 sequences. (Running on oeis4.)