A248422 Even integers concatenated with themselves.

22, 44, 66, 88, 1010, 1212, 1414, 1616, 1818, 2020, 2222, 2424, 2626, 2828, 3030, 3232, 3434, 3636, 3838, 4040, 4242, 4444, 4646, 4848, 5050, 5252, 5454, 5656, 5858, 6060, 6262, 6464, 6666, 6868, 7070, 7272, 7474, 7676, 7878, 8080, 8282, 8484, 8686, 8888, 9090, 9292, 9494, 9696, 9898, 100100

Offset

1,1

Comments

Bisection of A020338.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Formula

a(n) = 2*n*10^ceiling(log_10(2*n)) + 2*n. - Tom Edgar, Oct 21 2014

Mathematica

FromDigits[Flatten[IntegerDigits/@#]]&/@Partition[With[{c=2*Range[ 50]}, Riffle[c, c]], 2] (* or *) Table[n*10^IntegerLength[n]+n, {n, 2, 100, 2}] (* Harvey P. Dale, Jun 11 2019 *)

Prog

(PARI) a(n) = eval(concat(Str(2*n), Str(2*n))); \\ Michel Marcus, Oct 06 2014
(Magma) [Seqint(Intseq(n) cat Intseq(n)): n in [2..100 by 2]]; // Vincenzo Librandi, Oct 21 2014

Crossrefs

Cf. A020338.

Sequence in context: A308125 A061832 A087396 * A071266 A038153 A033848

Adjacent sequences: A248419 A248420 A248421 * A248423 A248424 A248425

Keyword

nonn,base

Author

Lev Krasnovsky, Oct 06 2014

Status

approved