This site is supported by donations to The OEIS Foundation.

 Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing. Other ways to donate

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A298978 Lexicographic first sequence of positive integers such that a(n)*a(n+1) has a digit 8, and no term occurs twice. 9
 1, 8, 6, 3, 16, 5, 17, 4, 2, 9, 12, 7, 14, 13, 22, 19, 15, 32, 24, 20, 29, 27, 18, 10, 28, 11, 26, 23, 21, 38, 31, 35, 25, 33, 36, 30, 46, 40, 37, 34, 42, 39, 47, 44, 41, 45, 53, 54, 52, 49, 58, 48, 51, 55, 56, 43, 60, 63, 61, 62, 59, 65, 69, 70, 64, 57, 50, 76, 68, 66, 71, 73, 67, 72, 74, 77, 79, 82, 83, 86, 78, 75, 91, 80, 81, 84, 87, 90, 89 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A permutation of the positive integers. LINKS EXAMPLE a(1) = 1 is the least positive integer, and a(1) has no other constraint to satisfy. a(2) = 8 is the least positive integer > a(1) = 1 such that a(2)*a(1) = 8 has a digit 3. a(3) = 6 is the least positive integer not in {1, 8} such that a(3)*a(2) (= 48) has a digit 8: All smaller choices 2, 4, ..., 7 do not satisfy this. a(4) = 3 is the least positive integer not in {1, 6, 8} such that a(4)*a(3) (= 18) has a digit 8: The only smaller choice 2 does not satisfy this. PROG (PARI) A298978(n, f=1, d=8, a=1, u=[a])={for(n=2, n, f&&if(f==1, print1(a", "), write(f, n-1, " "a)); for(k=u[1]+1, oo, setsearch(u, k)&&next; setsearch(Set(digits(a*k)), d)&&(a=k)&&break); u=setunion(u, [a]); while(#u>1&&u[2]==u[1]+1, u=u[^1])); a} CROSSREFS Cf. A299402, A298974, ..., A298979: analog with digit 2, 4, ..., 9. Cf. A299957, A299969, ..., A299988 (analog with addition instead of multiplication, and different digits). Sequence in context: A084895 A154719 A263181 * A199151 A177154 A059631 Adjacent sequences:  A298975 A298976 A298977 * A298979 A298980 A298981 KEYWORD nonn,base AUTHOR M. F. Hasler, Feb 22 2018 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
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified December 6 08:53 EST 2019. Contains 329788 sequences. (Running on oeis4.)