A355967 Indices of the primes that occur in A104589.

1, 3, 6, 25, 104, 634, 1236, 22613, 103409, 929044, 6298419, 80396036, 843325558, 5843115733, 24428345613, 515211289906, 4021634909249, 77930896716918, 387592118891917, 53467625139656294, 258820291307490689, 2600667638804262010, 29899374277934530878

Offset

1,2

Links

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

Example

The primes in A104589 are 2, 5, 13, 97, ... with prime indices 1, 3, 6, 25, ...

Mathematica

s[1] = 1; s[n_] := s[n] = s[n - 1] + Sum[If[CompositeQ[s[k]], 0, s[k]], {k, 1, n - 1}]; PrimePi[Select[s /@ Range[200], PrimeQ[#] &]] (* Amiram Eldar, Jul 21 2022 *)

Prog

(PARI) lista(nn) = my(last=1, s = 1, list = List()); for (n=2, nn, last += s; if (isprime(last), s += last; listput(list, primepi(last))); ); Vec(list);
(Python)
from sympy import isprime, primepi
from itertools import islice
def A355967_gen(): # generator of terms
    a, b = 1, 1
    while True:
        a += b
        if isprime(a):
            b += a
            yield primepi(a)
A355967_list = list(islice(A355967_gen(), 14)) # Chai Wah Wu, Jun 03 2024

Crossrefs

Cf. A000040, A000720, A104589, A355958.

Sequence in context: A266549 A057730 A350752 * A074432 A212650 A297572

Adjacent sequences: A355964 A355965 A355966 * A355968 A355969 A355970

Keyword

nonn

Author

Michel Marcus, Jul 21 2022

Extensions

a(14)-a(20) from Amiram Eldar, Jul 21 2022

a(21)-a(23) from Chai Wah Wu, Jun 03 2024

Status

approved