A019520 a(n) is the concatenation of the first n positive even numbers.

2, 24, 246, 2468, 246810, 24681012, 2468101214, 246810121416, 24681012141618, 2468101214161820, 246810121416182022, 24681012141618202224, 2468101214161820222426, 246810121416182022242628, 24681012141618202224262830, 2468101214161820222426283032

Offset

1,1

References

H. Ibstedt, A Few Smarandache Sequences, Smarandache Notions Journal, Vol. 8, No. 1-2-3, 1997, 170-183.

F. Smarandache, "Collected Papers", Vol. II, Tempus Publ. Hse., Bucharest, Romania, 1996.

S. Smarandoiu, Convergence of Smarandache continued fractions, Abstract 96T-11-195, Abstracts Amer. Math. Soc., 17 (No. 4, 1996), 680.

Links

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

Eric Weisstein's World of Mathematics, Consecutive Number Sequences

Formula

Lim_{n->oo} A019519(n)/a(n) = 0 (see A067095). - Bernard Schott, Dec 18 2021

Mathematica

Table[FromDigits[Flatten[IntegerDigits/@(2Range[n])]], {n, 20}] (* Harvey P. Dale, Mar 24 2013 *)

Prog

(Python)
def a(n): return int("".join(str(2*i) for i in range(1, n+1)))
print([a(n) for n in range(1, 17)]) # Michael S. Branicky, Dec 18 2021

Crossrefs

Cf. A019519 (similar, with odd numbers), A067095, A108728.

Sequence in context: A215929 A132596 A099669 * A300400 A187584 A173228

Adjacent sequences: A019517 A019518 A019519 * A019521 A019522 A019523

Keyword

base,nonn,easy,less

Author

R. Muller

Extensions

More terms from Erich Friedman

More terms from Harvey P. Dale, Mar 24 2013

Status

approved