A261618 Concatenation of n, n+1 and n.

121, 232, 343, 454, 565, 676, 787, 898, 9109, 101110, 111211, 121312, 131413, 141514, 151615, 161716, 171817, 181918, 192019, 202120, 212221, 222322, 232423, 242524, 252625, 262726, 272827, 282928, 293029, 303130, 313231, 323332, 333433, 343534, 353635, 363736

Offset: 1

Author

José de Jesús Camacho Medina, Sep 09 2015

Keywords

• nonn
• base

Comments

787, 9109, 111211, 131413, ... are primes. - N. J. A. Sloane, Sep 21 2015

Examples

			a(1) = concatenation(1, 2, 1) = 121.
a(10) = concatenation(10, 11, 10) = 101110.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A134810, A068660.

Programs

Magma

[Seqint(Intseq(n) cat Intseq(n+1) cat Intseq(n)):n in [1..36]]; // Marius A. Burtea, Dec 29 2019

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 *)

PARI

a(n) = eval(concat(Str(n), concat(Str(n+1), Str(n)))); \\ Michel Marcus, Sep 10 2015

Extensions

More terms from Michel Marcus, Sep 10 2015