login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A235497 2n concatenated with n. 6
21, 42, 63, 84, 105, 126, 147, 168, 189, 2010, 2211, 2412, 2613, 2814, 3015, 3216, 3417, 3618, 3819, 4020, 4221, 4422, 4623, 4824, 5025, 5226, 5427, 5628, 5829, 6030, 6231, 6432, 6633, 6834, 7035, 7236, 7437, 7638, 7839, 8040, 8241, 8442, 8643, 8844, 9045 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All terms are divisible by 3. - Michel Marcus, Sep 21 2015

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = 2*n*10^floor(log_10(n) + 1) + n.

MATHEMATICA

nxt[n_] := Module[{idn = IntegerDigits[n], idn2 = IntegerDigits[2 n]}, FromDigits[Join[idn2, idn]]]; Array[nxt, 50] (* Librandi *)

Table[FromDigits[Join[IntegerDigits[2n], IntegerDigits[n]]], {n, 40}] (* Alonso del Arte, Sep 13 2014 *)

PROG

(MAGMA) [Seqint(Intseq(n) cat Intseq(2*n)): n in [1..50]];

(Maxima) makelist(2*n*10^floor(log(n)/log(10) + 1) + n, n, 50); /* Bruno Berselli, Feb 06 2014, using the closed form added from Alois P. Heinz on Feb 05 2014 */

(PARI) a(n) = eval(Str(2*n, n)); \\ Michel Marcus, Sep 21 2015

CROSSREFS

Cf. A019550.

Sequence in context: A089059 A114384 A008603 * A086794 A001682 A180963

Adjacent sequences:  A235494 A235495 A235496 * A235498 A235499 A235500

KEYWORD

nonn,base,easy

AUTHOR

Vincenzo Librandi, Feb 04 2014

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 14 14:31 EDT 2019. Contains 328019 sequences. (Running on oeis4.)