A332657 - OEIS

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

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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 A375154 A084967

Adjacent sequences: A332654 A332655 A332656 * A332658 A332659 A332660

KEYWORD

nonn,easy

AUTHOR

Adnan Baysal, Feb 18 2020

STATUS

approved