A078395 a(1) = 1, a(n) for n > 1 is the smallest multiple of a(n-1) that begins with the reverse concatenation from n to 1.

1, 21, 3213, 4321485, 5432106645, 6543211466594880, 76543214032699698271680, 8765432112983964669342594296640, 9876543213798659527816605720220081111680

Offset

1,2

Links

Table of n, a(n) for n=1..9.

Example

For n = 3 we have a(n-1) = a(2) = 21; 153*21 = 3213 is the smallest multiple of a(2) that begins with 321, so a(3) = 3213.

Prog

(PARI) {print1(a=1, ", "); for(n=2, 9, k=floor(log(a)/log(10))+1; v=Str(1); for(i=2, n, v=concat(Str(i), v)); s=eval(v); t=s+1; m=floor(log(s)/log(10))+1; d=k-m; s=s*10^d; t=t*10^d; b=1; j=d; while(b>0, q=floor(s/a); while(b>0&&(p=q*a)<t, if(p>=s, print1(p, ", "); b=0, q++)); s=10*s; t=10*t); a=p)}

Crossrefs

Cf. A078296, A078396, A078397.

Sequence in context: A189447 A098724 A326295 * A340331 A370085 A202980

Adjacent sequences: A078392 A078393 A078394 * A078396 A078397 A078398

Keyword

base,nonn

Author

Amarnath Murthy, Nov 26 2002

Extensions

Edited and extended by Klaus Brockhaus, Dec 06 2002

Status

approved