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

Author

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

Keywords

• nonn
• base
• easy

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

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

Programs

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 *)

PARI

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

Extensions

More terms from Michel Marcus, Mar 03 2014