A317391 Positive integers that have a unique representation of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.

1, 3, 4, 6, 8, 9, 10, 12, 13, 14, 16, 17, 18, 19, 20, 21, 22, 24, 30, 32, 34, 38, 39, 42, 44, 45, 46, 48, 53, 54, 55, 58, 59, 60, 62, 64, 65, 68, 69, 70, 72, 73, 74, 75, 76, 79, 80, 83, 84, 86, 90, 92, 93, 94, 98, 99, 100, 101, 102, 104, 105, 107, 108, 109

Offset

1,2

Links

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

Formula

A317241(a(n)) = 1.

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<2
        do r:= r+b((n-1)/p, s union {p}) od; `if`(r<2, r, 2)
      fi
    end:
a:= proc(n) option remember; local k; for k from
     `if`(n=1, 1, 1+a(n-1)) while b(k, {})<>1 do od; k
    end:
seq(a(n), n=1..100);

Crossrefs

Column k=1 of A317390.

Cf. A317241.

Sequence in context: A090864 A118300 A263098 * A134745 A183867 A182829

Adjacent sequences: A317388 A317389 A317390 * A317392 A317393 A317394

Keyword

nonn

Author

Alois P. Heinz, Jul 27 2018

Status

approved