A356839 a(n) = A005132(2*n) + A005132(2*n+1).

1, 9, 9, 33, 33, 33, 33, 33, 33, 105, 105, 59, 59, 59, 59, 59, 125, 191, 191, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117, 117, 381, 381, 381, 381, 381, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 227, 429, 631, 631, 631, 631, 191, 417, 873, 873

Offset: 0

Author

Paul Curtz, Aug 31 2022

Keywords

• nonn

Links

• Michel Marcus, Table of n, a(n) for n = 0..9999
• Index entries for sequences related to Recamán's sequence.

Crossrefs

Cf. A005132.

Programs

Mathematica

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] + r[2*n + 1]; Array[a, 100, 0] (* Amiram Eldar, Sep 02 2022 *)

PARI

recaman(N)={ my(s, t, v=vector(N)); for(n=1, N, s=bitor(s, 1<A005132
lista(nn) = my(v=recaman(2*nn+2)); vector(nn, k, v[2*k] + v[2*k-1]); \\ Michel Marcus, Sep 02 2022

Python

from itertools import count, islice
def A356839_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 n&1:
            yield a+b
A356839_list = list(islice(A356839_gen(),70)) # Chai Wah Wu, Sep 15 2022