A080404 a(n)=A007947[A055932(n)]; the sequence consists of primorial numbers;.

2, 2, 6, 2, 6, 2, 6, 6, 30, 2, 6, 6, 6, 30, 2, 6, 30, 6, 6, 30, 2, 6, 30, 6, 30, 6, 210, 6, 30, 2, 30, 6, 30, 6, 30, 6, 210, 6, 30, 30, 6, 2, 30, 6, 30, 210, 6, 30, 30, 6, 30, 210, 6, 30, 30, 6, 2, 210, 30, 6, 30, 210, 6, 30, 30, 6, 210, 30, 6, 30, 210, 6, 30, 210, 30, 6, 2, 210, 30, 30, 6

Offset

1,1

Links

Michael De Vlieger, Table of n, a(n) for n = 1..10000

Mathematica

With[{P = FoldList[Times, Prime@ Range@ Max@ #]}, Map[P[[#]] &, #]] &@ Map[PrimeNu@ # &, Select[Range[10^4], Last[#] == Length[#] &@ PrimePi@ FactorInteger[#][[All, 1]] &]] (* Michael De Vlieger, Feb 06 2020 *)

Prog

(Python)
from math import prod
from itertools import count
from functools import lru_cache
from sympy import prime, integer_log, primorial, primefactors
from oeis_sequences.OEISsequences import bisection
def A080404(n):
    @lru_cache(maxsize=None)
    def g(x, m): return sum(g(x//(prime(m)**i), m-1) for i in range(1, integer_log(x, prime(m))[0]+1)) if m-1 else x.bit_length()-1
    def f(x):
        c = n+x
        for k in count(1):
            if primorial(k)>x:
                break
            c -= g(x, k)
        return c
    return prod(primefactors(bisection(f, n+1, n+1))) # Chai Wah Wu, Mar 18 2026

Crossrefs

Cf. A007947, A002110, A055932.

Sequence in context: A071796 A121699 A379493 * A379325 A378202 A247451

Adjacent sequences: A080401 A080402 A080403 * A080405 A080406 A080407

Keyword

nonn

Author

Labos Elemer, Mar 19 2003

Status

approved