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
KEYWORD
nonn,base
AUTHOR
Lev Krasnovsky, Oct 06 2014
STATUS
approved