OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..1000
EXAMPLE
81 is a term since 81 = 3^4, 85 = 5 * 17, and 3 = prime(2), 5 = prime(3), 17 = prime(7) and 83 = prime(23) are all prime-indexed primes.
MATHEMATICA
q[n_] := AllTrue[FactorInteger[n][[;; , 1]], PrimeQ[PrimePi[#]] &]; q[1] = True; v = q /@ {1, 3, 5}; seq = {}; Do[If[And @@ v, AppendTo[seq, k - 6]]; v = Join[Rest[v], {q[k]}], {k, 7, 10^5, 2}]; seq
PROG
(PARI) isokf(k) = my(f = factor(k)[, 1]); sum(i=1, #f, isprime(primepi(f[i]))) == #f; \\ A076610
isok(k) = (k % 2) && isokf(k) && isokf(k+2) && isokf(k+4); \\ Michel Marcus, Sep 16 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Amiram Eldar, Sep 16 2022
STATUS
approved