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

Author

Lev Krasnovsky, Oct 06 2014

Keywords

• nonn
• base

Comments

Bisection of A020338.

Links

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

Crossrefs

Cf. A020338.

Programs

Magma

[Seqint(Intseq(n) cat Intseq(n)): n in [2..100 by 2]]; // Vincenzo Librandi, 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 *)

PARI

a(n) = eval(concat(Str(2*n), Str(2*n))); \\ Michel Marcus, Oct 06 2014

Formula

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