A171915 Van Eck sequence (cf. A181391) starting with a(1) = 5.

5, 0, 0, 1, 0, 2, 0, 2, 2, 1, 6, 0, 5, 12, 0, 3, 0, 2, 9, 0, 3, 5, 9, 4, 0, 5, 4, 3, 7, 0, 5, 5, 1, 23, 0, 5, 4, 10, 0, 4, 3, 13, 0, 4, 4, 1, 13, 5, 12, 35, 0, 8, 0, 2, 36, 0, 3, 16, 0, 3, 3, 1, 16, 5, 16, 2, 12, 18, 0, 10, 32, 0, 3, 12, 7, 46, 0, 5, 14, 0, 3, 8, 30, 0, 4, 40, 0, 3, 7

Offset: 1

Author

N. J. A. Sloane, Oct 22 2010

Keywords

• nonn

Comments

A van Eck sequence is defined recursively by a(n+1) = min { k > 0 | a(n-k) = a(n) } or 0 if this set is empty, i.e., a(n) does not appear earlier in the sequence. - M. F. Hasler, Jun 15 2019

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..10001

Crossrefs

Cf. A181391, A171911, ..., A171918 (same but starting with 0, 1, ..., 8).

Programs

PARI

A171915_vec(N, a=5, i=Map())={vector(N, n, a=if(n>1, iferr(n-mapget(i, a), E, 0)+mapput(i, a, n), a))} \\ M. F. Hasler, Jun 15 2019

Python

A171915_list, l = [5, 0], 0
for n in range(1, 10**4):
    for m in range(n-1, -1, -1):
        if A171915_list[m] == l:
            l = n-m
            break
    else:
        l = 0
    A171915_list.append(l) # Chai Wah Wu, Jan 02 2015

Extensions

Name and other sections edited by M. F. Hasler, Jun 15 2019