OFFSET
1,1
COMMENTS
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
EXAMPLE
a(1) = 33331 because Concat(3,3,3,1) = 3331 which is in A000040.
MAPLE
A210720 := proc(n)
local p;
[n, n, n, n, 1] ;
p := digcatL(%) ;
if isprime(p) then
printf("%d, ", p) ;
end if;
end proc:
for n from 1 to 400 do
A210720(n) ;
end do: # R. J. Mathar, Feb 10 2013
MATHEMATICA
Select[Table[FromDigits[Flatten[{IntegerDigits[n], IntegerDigits[n], IntegerDigits[n], IntegerDigits[n], IntegerDigits[1], {}}]], {n, 200}], PrimeQ] (* Vincenzo Librandi, Mar 15 2013 *)
Select[Table[FromDigits[Join[Flatten[IntegerDigits/@PadRight[{}, 4, n]], {1}]], {n, 200}], PrimeQ] (* Harvey P. Dale, Oct 16 2017 *)
PROG
(Magma) [nnnn1: n in [1..200] | IsPrime(nnnn1) where nnnn1 is Seqint([1] cat Intseq(n) cat Intseq(n) cat Intseq(n) cat Intseq(n))]; // Vincenzo Librandi, Mar 15 2013
CROSSREFS
KEYWORD
nonn,base,easy,changed
AUTHOR
Jonathan Vos Post, Jan 29 2013
STATUS
approved