A158849 -id:A158849 - cp's OEIS frontend

A158859 a(n) is formed by 2n+1 concatenations of the digit 2r+1 where n=r (mod 5).

1, 333, 55555, 7777777, 999999999, 11111111111, 3333333333333, 555555555555555, 77777777777777777, 9999999999999999999, 111111111111111111111, 33333333333333333333333

Offset: 0

Paul Curtz, Mar 28 2009

One 1, three 3's, five 5's, seven 7's, nine 9's, eleven 1's, thirteen 3's,

Cf. A158849.

Definition modified by R. J. Mathar, Apr 06 2009

A267327 a(n) = decimal expansion of (n-1) prepended n times to the decimal expansion of n (n > 0).

Original entry on oeis.org

1, 112, 2223, 33334, 444445, 5555556, 66666667, 777777778, 8888888889, 999999999910, 101010101010101010101011, 11111111111111111111111112, 1212121212121212121212121213, 131313131313131313131313131314, 14141414141414141414141414141415, 1515151515151515151515151515151516

Offset: 1

Mikk Heidemaa, Jan 13 2016

These terms are primes: a(7), a(19), a(989), a(1187), a(4183); see A267237.

			a(3) = 2223 ('3-1' prepended 3 times to '3').

Cf. A000461, A158849, A158859, A267237.

Table[ FromDigits[ StringJoin@@ ToString/@ PadLeft[{n}, n+1, n-1]], {n, 50}](* Or *)
FromDigits/@ Table[ Nest[ ToString[n] <> #&, ToString[n+1], n+1], {n, 0, 50}]

a(n) = (10^(n+1)*(n-1) - n + 10) / 9 (n <= 9).

a(n) = Sum_{i=0...n+1} (n*10^(i*(floor(log(10, n+1)) + 1))) + 1 (n <> 10^k, k > 0), i.e. doesn't give correctly the terms ending with 0.

cp's OEIS Frontend

A158859 a(n) is formed by 2n+1 concatenations of the digit 2r+1 where n=r (mod 5).

Views

Author

Keywords

Comments

Crossrefs

Extensions

A267327 a(n) = decimal expansion of (n-1) prepended n times to the decimal expansion of n (n > 0).

Views

Author

Keywords

Comments

Examples

Crossrefs

Programs

Mathematica

Formula