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A317397 Positive integers that have exactly seven representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes. 2
1613, 3321, 3336, 3368, 3741, 3914, 3979, 4082, 4126, 4219, 4561, 4777, 4798, 4824, 4929, 4936, 4948, 5083, 5314, 5371, 5559, 5656, 5825, 5877, 5946, 5986, 6096, 6109, 6111, 6291, 6303, 6376, 6644, 6651, 6673, 6700, 6711, 6786, 6883, 6886, 6917, 6920, 7036 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Alois P. Heinz, Table of n, a(n) for n = 1..20000

FORMULA

A317241(a(n)) = 7.

MAPLE

b:= proc(n, s) option remember; local p, r; if n=1 then 1 else r:=0;

      for p in numtheory[factorset](n-1) minus s while r<8

        do r:= r+b((n-1)/p, s union {p}) od; `if`(r<8, r, 8)

      fi

    end:

a:= proc(n) option remember; local k; for k from

     `if`(n=1, 1, 1+a(n-1)) while b(k, {})<>7 do od; k

    end:

seq(a(n), n=1..100);

CROSSREFS

Column k=7 of A317390.

Cf. A317241.

Sequence in context: A023685 A301938 A205832 * A236060 A231048 A231423

Adjacent sequences:  A317394 A317395 A317396 * A317398 A317399 A317400

KEYWORD

nonn

AUTHOR

Alois P. Heinz, Jul 27 2018

STATUS

approved

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Last modified May 12 19:15 EDT 2021. Contains 343829 sequences. (Running on oeis4.)