A038396 Concatenate first n even numbers in reverse order.

2, 42, 642, 8642, 108642, 12108642, 1412108642, 161412108642, 18161412108642, 2018161412108642, 222018161412108642, 24222018161412108642, 2624222018161412108642, 282624222018161412108642, 30282624222018161412108642, 3230282624222018161412108642

Offset

1,1

Comments

F. Smarandache conjectures that a(n) is never a perfect power (see link sequence 163 page 80). - Michel Marcus, Mar 03 2014

References

Mihaly Bencze [Beneze], L. Tutescu, Some Notions and Questions in Number Theory, Sequence 4.

Links

Table of n, a(n) for n=1..16.

Florentin Smarandache, Sequences of Numbers Involved in Unsolved Problems, arXiv:math/0604019 [math.GM], 2006.

Mathematica

Join[{s = 2}, Table[s = FromDigits[Flatten[IntegerDigits[{n, s}]]], {n, 4, 26, 2}]] (* Jayanta Basu, Jul 14 2013 *)
Table[FromDigits[Flatten[IntegerDigits/@Range[2n, 2, -2]]], {n, 20}] (* Harvey P. Dale, Jun 11 2017 *)

Prog

(PARI) a(n) = concat(vector(n, i, Str(2*n - (2*i)+2))); \\ Michel Marcus, Mar 03 2014

Crossrefs

Sequence in context: A180425 A140170 A318247 * A287328 A276923 A308526

Adjacent sequences: A038393 A038394 A038395 * A038397 A038398 A038399

Keyword

nonn,base,easy

Author

M. I. Petrescu (mipetrescu(AT)yahoo.com)

Extensions

More terms from Michel Marcus, Mar 03 2014

Status

approved