A332657 Alternate adding and multiplying prime numbers: a(2n) = a(2n-1) * prime(2n+1) and a(2n-1) = a(2n) + prime(2n-2) for n >= 1.

5, 25, 32, 352, 365, 6205, 6224, 143152, 143181, 4438611, 4438648, 181984568, 181984611, 8553276717, 8553276770, 504643329430, 504643329491, 33811103075897, 33811103075968, 2468210524545664, 2468210524545743, 204861473537296669, 204861473537296758

Offset

1,1

Links

Table of n, a(n) for n=1..23.

Example

a(1) = 2 + 3 = 5;
a(2) = 5 * 5 = 25;
a(3) = 25 + 7 = 32;
...
a(40) = 2714410084880275101596278688487175846.

Prog

(Python)
from sympy import primerange
p = list(primerange(1, 200))
def a(n):
    out = p[0] + p[1]
    for i in range(1, n):
        if i % 2:
            out *= p[i + 1]
        else:
            out += p[i + 1]
    return out
for n in range(1, 25):
    print(a(n), end=", ")

Crossrefs

Cf. A047905, A047904, A077138, A222559, A332659, A332660.

Sequence in context: A291755 A018639 A029475 * A070391 A084967 A249827

Adjacent sequences: A332654 A332655 A332656 * A332658 A332659 A332660

Keyword

nonn,easy

Author

Adnan Baysal, Feb 18 2020

Status

approved