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 A096302 Number of combinations of two natural numbers that together have n digits. 1
 81, 1620, 24300, 324000, 4050000, 48600000, 567000000, 6480000000, 72900000000, 810000000000, 8910000000000, 97200000000000, 1053000000000000, 11340000000000000, 121500000000000000, 1296000000000000000 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 2..100 FORMULA a(n) = Sum_{i=0..n-1} binomial(n-1, i)*9^(i+1)*i. a(n) = 81*(n-1)*10^(n-2). - Vladeta Jovovic, Jun 26 2004 MATHEMATICA f[n_] := Sum[Binomial[n - 1, i]*9^(i + 1)*i, {i, 0, n}]; Table[ a[n], {n, 2, 17}] (* Robert G. Wilson v, Jun 30 2004 *) PROG (Magma) [81*(n-1)*10^(n-2): n in [2..30]]; // Vincenzo Librandi, Jun 06 2011 CROSSREFS Cf. A053541. Sequence in context: A284057 A237559 A223279 * A297681 A237404 A237549 Adjacent sequences: A096299 A096300 A096301 * A096303 A096304 A096305 KEYWORD nonn,easy,base AUTHOR Hagai Helman (Helman(AT)actcom.net.il), Jun 25 2004 EXTENSIONS More terms from Robert G. Wilson v, Jun 30 2004 STATUS approved

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Last modified August 6 18:55 EDT 2024. Contains 374981 sequences. (Running on oeis4.)