A317396 Positive integers that have exactly six representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.

664, 1956, 2058, 2092, 2094, 2283, 2381, 2388, 2432, 2466, 2533, 2624, 2701, 2775, 2822, 2853, 2976, 3070, 3193, 3220, 3316, 3326, 3436, 3442, 3461, 3485, 3529, 3568, 3571, 3576, 3620, 3746, 3784, 3785, 3797, 3826, 3839, 3913, 4005, 4026, 4031, 4213, 4234

Offset

1,1

Links

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

Formula

A317241(a(n)) = 6.

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<7
        do r:= r+b((n-1)/p, s union {p}) od; `if`(r<7, r, 7)
      fi
    end:
a:= proc(n) option remember; local k; for k from
     `if`(n=1, 1, 1+a(n-1)) while b(k, {})<>6 do od; k
    end:
seq(a(n), n=1..100);

Crossrefs

Column k=6 of A317390.

Cf. A317241.

Sequence in context: A243889 A105978 A208180 * A211839 A171395 A069426

Adjacent sequences: A317393 A317394 A317395 * A317397 A317398 A317399

Keyword

nonn

Author

Alois P. Heinz, Jul 27 2018

Status

approved