login
A123923
a(1)=1. a(n) = (highest term among first n-1 terms of sequence which divides n)-th integer from among those integers not occurring among the first n-1 terms of the sequence.
1
1, 2, 3, 5, 9, 7, 13, 6, 17, 12, 4, 23, 25, 18, 15, 14, 33, 35, 8, 20, 24, 11, 45, 47, 49, 34, 29, 38, 57, 40, 10, 30, 65, 67, 69, 48, 16, 75, 42, 79, 19, 83, 21, 43, 89, 61, 93, 95, 97, 64, 54, 50, 22, 107, 46, 55, 113, 78, 26, 82, 121, 28, 71, 127, 129, 90, 133, 92, 137, 96
OFFSET
1,2
COMMENTS
Sequence is likely a permutation of the positive integers.
LINKS
EXAMPLE
3 is the largest integer which occurs among the first 5 terms of the sequence and which divides 6. So for a(6) we want the 3rd integer from among those positive integers not among the first 5 terms of the sequence (i.e. we want the 3rd integer from among 4,6,7,8,10,...). So a(6) = 7.
MATHEMATICA
f[l_List] := Block[{k = 0, c = Max @@ Select[l, Mod[Length[l] + 1, # ] == 0 &]}, While[c > 0, k++; While[MemberQ[l, k], k++ ]; c--; ]; Append[l, k]]; Nest[f, {1}, 72] (* Ray Chandler, Nov 23 2006 *)
Fold[Append[#1, Complement[Range[Max@#1 + (r = Max@Intersection[#1, Divisors@#2])], #1][[r]]] &, {1}, Range[2, 70]] (* Ivan Neretin, Oct 20 2018 *)
CROSSREFS
Sequence in context: A011026 A374531 A069805 * A045965 A323390 A346096
KEYWORD
nonn
AUTHOR
Leroy Quet, Nov 20 2006
EXTENSIONS
Extended by Ray Chandler, Nov 23 2006
STATUS
approved