A355958 Positions where primes occur in A104589.
2, 3, 4, 8, 12, 18, 19, 35, 39, 47, 53, 65, 75, 81, 84, 102, 109, 127, 131, 261, 265, 273, 283, 305, 323, 329, 350, 450, 456, 462, 492, 522, 562, 660, 664, 784, 904, 922, 1081, 1213, 1258, 1406, 1443, 1467, 1549, 1655, 1772, 1774, 1786, 1810, 1901, 1919, 2024, 2144, 2161
Offset: 1
Keywords
Examples
The 1st prime in A104589 is 2, and its position is 2, so a(1) = 2. The 2nd prime in A104589 is 5, and its position is 3, so a(2) = 3. The 3rd prime in A104589 is 13, and its position is 4, so a(3) = 4.
Programs
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Mathematica
s[1] = 1; s[n_] := s[n] = s[n - 1] + Sum[If[CompositeQ[s[k]], 0, s[k]], {k, 1, n - 1}]; Select[Range[2000], PrimeQ[s[#]] &] (* Amiram Eldar, Jul 21 2022 *) -
PARI
lista(nn) = my(last=1, s = 1, list = List()); for (n=2, nn, last += s; if (isprime(last), s += last; listput(list, n));); Vec(list);