This site is supported by donations to The OEIS Foundation.

 Annual appeal: Please make a donation to keep the OEIS running! Over 6000 articles have referenced us, often saying "we discovered this result with the help of the OEIS". Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A171785 Start with a(1) = 1; then a(n) = smallest number > a(n-1) such that a(n) divides concat(a(1), a(2), ..., a(n)). 7
 1, 2, 3, 5, 10, 12, 15, 20, 25, 30, 39, 44, 50, 100, 101, 125, 150, 188, 200, 220, 230, 250, 272, 304, 320, 370, 376, 400, 500, 525, 600, 615, 625, 1000, 1250, 1487, 1500, 1590, 1696, 1750, 2000, 2245, 2500, 3000, 3090, 3125, 3800, 4000, 5000, 5725, 6122, 7025 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Primes appearing so far are 2, 3, 5, 101, 1487. LINKS R. G. Wilson v, Table of n, a(n) for n = 1..584 EXAMPLE 1: 1 divides 1 1,2: 2 divides 12 1,2,3: 3 divides 123 1,2,3,4: 4 does NOT divide 1234, so 1,2,3,5: 5 divides 1235 etc. MAPLE with(numtheory); P:=proc(q) local a, n; a:=0; for n from 1 to q do if type((a*10^(1+ilog10(n))+n)/n, integer) then a:=a*10^(1+ilog10(n))+n; print(n); fi; od; end: P(10^5); # Paolo P. Lava, Nov 27 2014 MATHEMATICA f[s_List] := Block[{k = s[[ -1]] + 1, conc = FromDigits[Flatten@ IntegerDigits@s]}, While[ Mod[conc*10^Floor[ Log[10, k] + 1] + k, k] != 0, k++ ]; Append[s, k]]; Nest[f, {1}, 51] (* Robert G. Wilson v, Oct 14 2010 *) nxt[{a_, c_}]:=Module[{k=a+1}, While[!Divisible[c*10^IntegerLength[k]+ k, k], k++]; {k, c*10^IntegerLength[k]+k}]; Transpose[NestList[nxt, {1, 1}, 60]][[1]] (* Harvey P. Dale, Mar 08 2015 *) CROSSREFS Sequence in context: A039022 A182402 A079251 * A050051 A252353 A241167 Adjacent sequences:  A171782 A171783 A171784 * A171786 A171787 A171788 KEYWORD nonn,base AUTHOR David Scambler, Sep 30 2010 EXTENSIONS More terms from Robert G. Wilson v, Oct 14 2010 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.