A356870 a(n) = (A005132(2*n-1) + A005132(2*n))/4.

1, 2, 5, 8, 8, 8, 8, 8, 17, 26, 26, 15, 15, 15, 15, 15, 48, 48, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 29, 62, 95, 95, 95, 95, 95, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 57, 158, 158, 158, 158, 103, 48, 161, 218, 218, 99, 99, 99, 99, 99, 35, 35, 168, 100, 100, 100

Offset

1,2

Links

Michel Marcus, Table of n, a(n) for n = 1..10000

Mathematica

r[-1] = r[0] = 0; r[n_] := r[n] = If[(d = r[n - 1] - n) >= 0 && FreeQ[Array[r, n, 0], d], d, r[n - 1] + n]; a[n_] := (r[2*n - 1] + r[2*n])/4; Array[a, 100] (* Amiram Eldar, Sep 02 2022 *)

Prog

(PARI) recaman(N)={ my(s, t, v=vector(N)); for(n=1, N, s=bitor(s, 1<<t += if( t<=n || bittest(s, t-n), n, -n)); v[n]=t); v; } \\ adapted from A005132
lista(nn) = my(v=recaman(2*nn+2)); vector(nn, k, v[2*k-1] + v[2*k])/4; \\ Michel Marcus, Sep 13 2022
(Python)
from itertools import count, islice
def A356870_gen(): # generator of terms
    b, aset = 0, set()
    for n in count(1):
        aset.add(b)
        a, b = b, c if (c:=b-n)>=0 and c not in aset else b+n
        if not n&1:
            yield a+b>>2
A356870_list = list(islice(A356870_gen(), 30)) # Chai Wah Wu, Sep 15 2022

Crossrefs

Cf. A005132, A356839.

Sequence in context: A019824 A284868 A019772 * A351391 A046825 A250320

Adjacent sequences: A356867 A356868 A356869 * A356871 A356872 A356873

Keyword

nonn,look

Author

Paul Curtz, Sep 02 2022

Extensions

New name, data and offset from Michel Marcus, Sep 13 2022

Status

approved