A068090 - OEIS

A068090

Numbers n which divide the right concatenation of the first n even numbers.

1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 14, 15, 18, 20, 24, 25, 30, 35, 36, 39, 40, 45, 50, 60, 72, 75, 80, 90, 100, 120, 125, 144, 150, 180, 200, 204, 225, 240, 250, 300, 360, 375, 400, 450, 500, 507, 540, 585, 600, 624, 625, 675, 702, 720, 750, 780, 800, 804, 864, 900

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

LINKS

Table of n, a(n) for n=1..60.

EXAMPLE

The right concatenation of the first six even numbers is 24681012 and 6 divides this number. So 6 is a member of the sequence.

MAPLE

a := proc(n): if n=1 then RETURN(2) fi: 2*n+a(n-1)*10^(ceil(log[10](2*n+.01))) end: for n from 1 to 1000 do if a(n) mod n = 0 then printf(`%d, `, n) fi; od:

MATHEMATICA

concat[n_]:=FromDigits[Flatten[IntegerDigits/@Range[2, 2n, 2]]]; Select[ Range[700], Divisible[concat[#], #]&] (* Harvey P. Dale, Nov 02 2011 *)

CROSSREFS

Cf. A029455.

Sequence in context: A248888 A112587 A372916 * A172121 A094222 A164043

Adjacent sequences: A068087 A068088 A068089 * A068091 A068092 A068093

KEYWORD

base,easy,nonn

AUTHOR

Amarnath Murthy, Feb 19 2002

EXTENSIONS

Edited and extended by James A. Sellers, Feb 20, 2002

Offset corrected by Sean A. Irvine, Jan 25 2024

STATUS

approved