The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A069521 Smallest multiple of n with digit sum = 2, or 0 if no such number exists, e.g., a(3k)=0. 22
 2, 2, 0, 20, 20, 0, 1001, 200, 0, 20, 11, 0, 1001, 10010, 0, 2000, 100000001, 0, 1000000001, 20, 0, 110, 100000000001, 0, 200, 10010, 0, 100100, 100000000000001, 0, 0, 20000, 0, 1000000010, 10010, 0, 0, 10000000010, 0, 200, 0, 0, 0, 1100, 0 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n)=0 if n is a multiple of 3, 31, 37, 41, 43, 53, 67, 71, 79, or 83. - Ray Chandler, Jul 30 2003 LINKS Robert Israel, Table of n, a(n) for n = 1..2016 FORMULA From Robert Israel, Feb 11 2023: (Start) If n = 2^a * 5^b, a(n) = 2*10^max(a-1,b). Otherwise, if n = 2^a*5^b*c where c is in A043292, then a(n) = 10^max(a,b) * (1 + 10^A069531(c)). Otherwise a(n) = 0. (End) EXAMPLE a(7) = a(13) = 1001. Digit sum of 1001 = 2 and is the smallest such multiple of 7 and 13. a(17) = 100000001 = 17*5882353. MAPLE f:= proc(n) local a, b, c, k; a:= padic:-ordp(n, 2); b:= padic:-ordp(n, 5); c:= n/(2^a*5^b); if c = 1 then return 2*10^max(a-1, b) fi; k:= traperror(NumberTheory:-ModularLog(-1, 10, c)); if k = "no solutions exist" then 0 else 10^max(a, b) * (1 + 10^k) fi end proc: map(f, [\$1..50]); # Robert Israel, Feb 11 2023 CROSSREFS Cf. A043292, A069531. Sequence in context: A134085 A151339 A228273 * A245687 A228617 A119836 Adjacent sequences: A069518 A069519 A069520 * A069522 A069523 A069524 KEYWORD base,nonn AUTHOR Amarnath Murthy, Apr 01 2002 EXTENSIONS More terms from Ray Chandler, Jul 30 2003 STATUS approved

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

Last modified June 6 05:06 EDT 2023. Contains 363139 sequences. (Running on oeis4.)