OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
FORMULA
EXAMPLE
For n=0 we concatenate 3, 0, 0 and 3 to get 3003.
For n=10 we concatenate 3, 10, 10 and 3 to get 310103.
MAPLE
f:= n -> 9 + 9*10^(2*ilog10(n-1)+3)+(n-1)*(10+10^(2+ilog10(n-1))):
f(1):= 9009;
map(f, [$1..200]); # Robert Israel, May 09 2017
MATHEMATICA
With[{k = {9}}, Table[FromDigits@ Join[k, #, #, k] &@ IntegerDigits[n], {n, 0, 30}]] (* Michael De Vlieger, May 09 2017 *)
CROSSREFS
KEYWORD
easy,nonn,base
AUTHOR
Mark Hudson (mrmarkhudson(AT)hotmail.com), Jan 12 2005
STATUS
approved