OFFSET
1,1
COMMENTS
787, 9109, 111211, 131413, ... are primes. - N. J. A. Sloane, Sep 21 2015
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(1) = concatenation(1, 2, 1) = 121.
a(10) = concatenation(10, 11, 10) = 101110.
MAPLE
f:= n -> n + 10^(1+ilog10(n))*(n+1)+10^(2+ilog10(n)+ilog10(n+1))*n:
map(f, [$1..100]); # Robert Israel, Dec 29 2019
MATHEMATICA
Map[FromDigits@ Join[#1, #2, #1] & @@ IntegerDigits[#] &, Partition[Range@ 37, 2, 1]] (* Michael De Vlieger, Dec 29 2019 *)
PROG
(PARI) a(n) = eval(concat(Str(n), concat(Str(n+1), Str(n)))); \\ Michel Marcus, Sep 10 2015
(Magma) [Seqint(Intseq(n) cat Intseq(n+1) cat Intseq(n)):n in [1..36]]; // Marius A. Burtea, Dec 29 2019
CROSSREFS
KEYWORD
nonn,base
AUTHOR
José de Jesús Camacho Medina, Sep 09 2015
EXTENSIONS
More terms from Michel Marcus, Sep 10 2015
STATUS
approved