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

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A359007 a(n) = b(n-b(n)) where b is Van Eck's sequence A181391. 0
 0, 0, 0, 0, 1, 0, 2, 0, 2, 0, 0, 2, 0, 5, 1, 0, 0, 0, 2, 4, 0, 5, 0, 6, 0, 3, 0, 0, 2, 5, 0, 4, 14, 6, 3, 0, 6, 15, 5, 3, 9, 0, 5, 3, 0, 6, 5, 0, 3, 8, 3, 6, 0, 3, 2, 0, 0, 5, 9, 0, 4, 1, 0, 0, 3, 32, 0, 4, 11, 0, 7, 17, 0, 3, 11, 0, 2, 31, 6, 31, 0, 0, 6, 3, 0, 9, 2, 33, 3, 0, 3, 15, 0, 5 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,7 COMMENTS In Van Eck's sequence, b(n) is the distance between b(n-1) and the previous occurrence of b(n-1) there. Taking a(n) = b(n-b(n)) is therefore the distance between the second and third last occurrence of b(n-1) there. If b(n-1) has not yet occurred three times then the result is a(n) = 0 either by b(n)=0 when b(n-1) has only occurred once, or b(n-b(n)) = 0 when b(n-1) has only occurred twice. LINKS Table of n, a(n) for n=1..94. EXAMPLE b(14) is 2, so we count back two steps to b(12), which is 5. Therefore a(14) = 5. As b(14-1) = b(13) = 0, the three occurrences of 0's are separated by b(14) and b(12) = a(14), that is, 2 and 5 steps: . n: ... 5 6 7 8 9 10 11 12 13 14 15 16 ... . |<--------5-------->|<--2-->| | | | | | | b(n): ... 2, 0, 2, 2, 1, 6, 0, 5, 0, 2, 6, 5, ... | | v | a(14) = 5 <----- two steps back PROG (PARI) A181391_vec(N, a=0, i=Map())={vector(N, n, a=if(n>1, iferr(n-mapget(i, a), E, 0)+mapput(i, a, n)))}; lista(nn) = my(v = A181391_vec(nn)); vector(#v, k, v[k-v[k]]); \\ Michel Marcus, Dec 11 2022 CROSSREFS Cf. A181391. Sequence in context: A340683 A221645 A216176 * A128765 A193511 A254218 Adjacent sequences: A359004 A359005 A359006 * A359008 A359009 A359010 KEYWORD nonn,easy AUTHOR Tamas Sandor Nagy, Dec 10 2022 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 August 11 17:54 EDT 2024. Contains 375073 sequences. (Running on oeis4.)