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A357168
Starts of runs of at least 3 consecutive odd numbers whose prime factors are all prime-indexed primes.
3
1, 81, 121, 123, 153, 275, 1199, 1201, 1409, 1411, 2545, 3175, 4565, 5557, 5623, 6651, 7053, 8649, 11953, 15621, 16141, 16143, 20869, 22905, 28573, 36289, 39521, 51739, 52161, 56079, 56699, 56701, 63981, 76071, 77249, 79111, 105211, 125525, 144549, 153761, 167341
OFFSET
1,2
LINKS
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
Subsequence of A357167.
A357169 is a subsequence.
Sequence in context: A129151 A039546 A223020 * A253261 A280587 A273372
KEYWORD
nonn
AUTHOR
Amiram Eldar, Sep 16 2022
STATUS
approved