cp's OEIS Frontend

A317400 Positive integers that have exactly ten representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.

%I A317400 #4 Jul 27 2018 11:44:03
%S A317400 11306,13289,13693,16402,16446,16491,16699,17031,17113,17116,17263,
%T A317400 17576,18412,18602,19825,20023,20411,21022,21256,21676,21936,22271,
%U A317400 22543,22716,22764,23038,23233,23332,23353,23580,23599,23886,24036,24053,24064,24531,24646
%N A317400 Positive integers that have exactly ten representations of the form 1 + p1 * (1 + p2* ... * (1 + p_j)...), where [p1, ..., p_j] is a (possibly empty) list of distinct primes.
%H A317400 Alois P. Heinz, <a href="/A317400/b317400.txt">Table of n, a(n) for n = 1..20000</a>
%F A317400 A317241(a(n)) = 10.
%p A317400 b:= proc(n, s) option remember; local p, r; if n=1 then 1 else r:=0;
%p A317400       for p in numtheory[factorset](n-1) minus s while r<11
%p A317400         do r:= r+b((n-1)/p, s union {p}) od; `if`(r<11, r, 11)
%p A317400       fi
%p A317400     end:
%p A317400 a:= proc(n) option remember; local k; for k from
%p A317400      `if`(n=1, 1, 1+a(n-1)) while b(k, {})<>10 do od; k
%p A317400     end:
%p A317400 seq(a(n), n=1..100);
%Y A317400 Column k=10 of A317390.
%Y A317400 Cf. A317241.
%K A317400 nonn
%O A317400 1,1
%A A317400 _Alois P. Heinz_, Jul 27 2018