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.

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

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: A301938 A352545 A205832 * A236060 A231048 A231423

Adjacent sequences: A317394 A317395 A317396 * A317398 A317399 A317400

Keyword

nonn

Author

Alois P. Heinz, Jul 27 2018

Status

approved